Add "day zero" experiment daily retention P3A metric

[DJAndries]

"Day zero" experiments will be performed in the future in an attempt to improve user retention. The experiments will involve small changes in the UI. Add daily retention metrics for measuring the results of the experiment.

If you are included in the A variant of the day zero experiment, how long ago did you install the browser?
Brave.DayZero.A.InstallTime

If you are not included in the B variant of the day zero experiment, how long ago did you install the browser?
Brave.DayZero.B.InstallTime

Values for the metric range from 0 to 30 days. The refcode will be included with the report.

cc @chrismore @timchilds

[kjozwiak]

The above requires 1.65.110 or higher for 1.65.x verification 👍 The above will also be verified/checked using brave/brave-variations#979 and will be pushed into production via brave/brave-variations#980 once 1.65.x is released.

[GeetaSarvadnya]

Verification PASSED on

Brave | 1.65.110 Chromium: 124.0.6367.29 (Official Build) (64-bit)
-- | --
Revision | 6271fdd3c799c0db71c1e6ca8c83888a7bbbfbd2
OS | Windows 10 Version 22H2 (Build 19045.4046)

• Verified the test plan from Add "day zero" experiment feature & metrics brave-core#22195

• Open brave and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics response value is 0 as expected
  

• Clean profile, launch brave using brave.exe --enable-features="BraveDayZeroExperiment:variant/a" and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics response value is 0 as expected
  

• Close the browser and set the sys date ahead by 7 days, relaunch brave and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics response value is 7 as expected'

• step 3, Close browser, advance system time by 14 days, start browser with --enable-features="BraveDayZeroExperiment:variant/b", ensure metric has value of 21, and Brave.DayZero.B.InstallTime does NOT exist

Example	Example

• step 4, Close browser advance system time by 14 days, start browser, ensure that the metric still has a value of 21 (to ensure that the metric was not updated internally).
  

• steps 5, 6- Start with fresh profile with --enable-features="BraveDayZeroExperiment:variant/b" switch and Ensure Brave.DayZero.B.InstallTime has a value of 0.
  

• step 7- Close browser, advance system time by 7 days, start browser, ensure metric has value of 7.
  

• step 8, Close browser, advance system time by 14 days, start browser without --enable-features="BraveDayZeroExperiment:variant/b", ensure metric has value of 21, and Brave.DayZero.A.InstallTime does NOT exist

Example	Example

• step 9, Close browser advance system time by 14 days, start browser, ensure that the metric still has a value of 21 (to ensure that the metric was not updated internally).
  

• Confirmed that the metrics only exist in the logs_constellation_prep_express pref.

[GeetaSarvadnya]

Verification INPROGRESS on Samsung Galaxy version 12 running Bravemonoarm64.apk_1.65.114

• Verified the test plan from Add "day zero" experiment feature & metrics brave-core#22195
• Open brave and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics isn't shown
  
• Clean profile, launch brave using brave.exe --enable-features="BraveDayZeroExperiment:variant/a" and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics response value is 0 as expected
  
• Close the browser and set the sys date ahead by 7 days, relaunch brave and open brave://local-state file and look for the metrics Brave.DayZero.A.InstallTime and ensured that the metrics response value is 7 as expected'
• step 3, Close browser, advance system time by 14 days, start browser with --enable-features="BraveDayZeroExperiment:variant/b", ensure metric has value of 21, and Brave.DayZero.B.InstallTime does NOT exist

Example	Example

• step 4, Close browser advance system time by 14 days, start browser, ensure that the metric still has a value of 21 (to ensure that the metric was not updated internally).
  

• steps 5, 6- Start with fresh profile with --enable-features="BraveDayZeroExperiment:variant/b" switch and Ensure Brave.DayZero.B.InstallTime has a value of 0.
  

• step 7- Close browser, advance system time by 7 days, start browser, ensure metric has value of 7.
  

• step 8, Close browser, advance system time by 14 days, start browser without --enable-features="BraveDayZeroExperiment:variant/b", ensure metric has value of 21, and Brave.DayZero.A.InstallTime does NOT exist

Example	Example

• step 9, Close browser advance system time by 14 days, start browser, ensure that the metric still has a value of 21 (to ensure that the metric was not updated internally).
  

• Confirmed that the metrics only exist in the logs_constellation_prep_express pref.

[GeetaSarvadnya]

Verification INPROGRESS on Vivo X70 Pro version 12 running Bravemonoarm64.apk_1.65.114

[GeetaSarvadnya]

@DJAndries I have verified the test plan from brave/brave-core#22195 and noticed that the metrics Brave.DayZero.A.InstallTime isn't shown on the local state file on Android. Steps followed are as below:

1. Clean profile 1.65.114
2. Enable developer options
3. Open QA preferences and enter the flag --enable-features="BraveDayZeroExperiment:variant/a" on Command Line String field via Developer options->QA preferences
4. Relaunch the browser
5. Open brave://version
6. Ensured that the StudyBraveDayZeroExperiment:GroupBraveDayZeroExperiment is shown under Active Variations via brave://version
7. Open brave://local-state file
8. Look for the metrics Brave.DayZero.A.InstallTime
9. Metrics is not shown
10. Close the browser and set the sys date ahead by 7 days
11. Relaunch the browser
12. Reload brave://local-state file
13. Look for the metrics Brave.DayZero.A.InstallTime
14. Metrics is not shown

cc: @hffvld

[DJAndries]

This issue cannot be QA'd effectively on Android, since the feature needs to be enabled upon first run. There is no easy way to do this on Android, currently.