xds: generic xds client ads stream tests

[purnesh42H]

RELEASE NOTES: None

[codecov]

Codecov Report

Attention: Patch coverage is 81.25000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 82.30%. Comparing base (d00f4ac) to head (19248d1).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
xds/internal/clients/xdsclient/ads_stream.go	73.91%	4 Missing and 2 partials ⚠️
xds/internal/clients/internal/testutils/channel.go	75.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8307      +/-   ##
==========================================
+ Coverage   82.22%   82.30%   +0.07%     
==========================================
  Files         419      419              
  Lines       41954    42025      +71     
==========================================
+ Hits        34497    34589      +92     
+ Misses       5995     5979      -16     
+ Partials     1462     1457       -5     

Files with missing lines	Coverage Δ
xds/internal/clients/xdsclient/xdsclient.go	80.25% <100.00%> (+2.05%)	⬆️
xds/internal/clients/internal/testutils/channel.go	89.28% <75.00%> (-10.72%)	⬇️
xds/internal/clients/xdsclient/ads_stream.go	79.77% <73.91%> (+0.14%)	⬆️

... and 29 files with indirect coverage changes

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[dfawley]

Please put this in an internal subdirectory and set it to an unexported function here.

[purnesh42H]

Done for both expiry and backoff

[dfawley]

I am going to defer to @easwars to review this since he has a lot more experience/familiarity with the original xdsclient and its tests.

[dfawley]

Is this moved from elsewhere? You have several "new" files with 2024, so unless they're copies, please update.

[purnesh42H]

yeah this is copied from internal and then modified. Similar to how done in previous PRs

[dfawley]

I see. That should make it a lot easier to review @easwars.

[purnesh42H]

These tests needs to be deleted from internal xdsclient as part of migration PR #8310 as they need to override internal resource watching implementation.