alts: Record network latency and pass it to the handshaker service.

[matthewstevenson88]

The corresponding field was added to the proto in grpc/grpc-proto#138.

@cesarghali Could you give me a quick gut check on whether this looks reasonable to you?

RELEASE NOTES: none

[codecov]

Codecov Report

Merging #6851 (366f3ab) into master (45624f0) will increase coverage by 0.12%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6851      +/-   ##
==========================================
+ Coverage   83.64%   83.76%   +0.12%     
==========================================
  Files         286      286              
  Lines       30786    30792       +6     
==========================================
+ Hits        25750    25793      +43     
+ Misses       3977     3944      -33     
+ Partials     1059     1055       -4     

Files	Coverage Δ
credentials/alts/internal/handshaker/handshaker.go	74.22% <100.00%> (+0.82%)	⬆️

... and 14 files with indirect coverage changes

[easwars]

@matthewstevenson88: Any reason this is in draft? Is this good to be looked at?

[matthewstevenson88]

Sorry for the delayed reply, busy week. :)

I just wanted a chance to fix up the vet-proto issues caused by me using an old version of the protoc tool. Should be all fixed now.

@easwars Would you be able to review?

[easwars]

I can do a pass for Go readability related stuff. But I don't know enough to review for correctness etc.

[matthewstevenson88]

Thanks @easwars. Added @cesarghali to take a first look.

[matthewstevenson88]

@easwars Would you mind taking a quick pass for readability now?

[easwars]

LGTM, modulo minor nits.

[easwars]

Is this change covered under #6857?

[matthewstevenson88]

Good call, sync-ed this branch.

[matthewstevenson88]

Thanks for the review @easwars!