[WIP] Use isAppContext to determine if we're in an embedded WebView…

[kollivier]

…on Win, Mac, and Android.

Summary

Fixes learningequality/kolibri-app#68 (comment)

Marking this as WIP until I can get built packages to try out in the apps.

Reviewer guidance

Check that within the app, download buttons do not appear, but that they do appear when run in the browser.

References

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Contributor Checklist

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Reviewer Checklist

• Automated test coverage is satisfactory
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[codecov]

Codecov Report

Merging #7663 (eebce9b) into release-v0.14.x (a69718c) will decrease coverage by 22.79%.
The diff coverage is 17.02%.

Impacted Files	Coverage Δ
...libri/core/assets/src/api-resources/contentNode.js	0.00% <0.00%> (ø)
...ibri/core/assets/src/api-resources/facilityTask.js	0.00% <0.00%> (ø)
kolibri/core/assets/src/api-resources/index.js	100.00% <ø> (ø)
...olibri/core/assets/src/mixins/commonCoreStrings.js	33.33% <ø> (ø)
...libri/core/assets/src/mixins/commonSyncElements.js	5.88% <0.00%> (-2.46%)	⬇️
...ri/core/assets/src/state/modules/core/mutations.js	35.71% <ø> (-3.18%)	⬇️
kolibri/core/assets/src/utils/appCapabilities.js	27.27% <0.00%> (ø)
kolibri/core/assets/src/utils/browserInfo.js	100.00% <ø> (ø)
kolibri/core/assets/src/utils/intl-locale-data.js	0.94% <0.00%> (-0.08%)	⬇️
kolibri/core/assets/src/views/AppBar.vue	60.86% <0.00%> (-9.14%)	⬇️
... and 453 more

[jonboiser]

isEmbddedWebView needs to be called as function on line 56 below

[kollivier]

Closing this PR as this approach will take more work than anticipated, and given that it is probably better to just focus on switching to isAppContext for all app checking, and use the capabilities system to allow the app to report whether or not it can download files.