xds/resolver: use dependency manager to get LDS and RDS

[eshitachandwani]

This change is part of A74 implementation.

This PR removes the listener and route watchers from resolver and changes it so that we get the resources from xds dependency manager.

Note : This also includes the changes from #8651 since the changes in this PR are dependent on that. The changes in this PR will reduce after #8651 is merged. The changes of this PR are in the following files only :

• xds_resolver.go
• xds_resolver_test.go
• helper_test.go

RELEASE NOTES: N/A

[codecov]

Codecov Report

❌ Patch coverage is 75.29412% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.36%. Comparing base (7be33f4) to head (aa3ea57).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/xds/xdsdependencymanager/watch_service.go	54.28%	8 Missing and 8 partials ⚠️
internal/xds/xdsclient/xdsresource/xdsconfig.go	0.00%	8 Missing ⚠️
...xds/xdsdependencymanager/xds_dependency_manager.go	89.47%	4 Missing and 4 partials ⚠️
internal/grpctest/tlogger.go	75.00%	4 Missing and 3 partials ⚠️
internal/xds/resolver/xds_resolver.go	85.71%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8687      +/-   ##
==========================================
+ Coverage   83.28%   83.36%   +0.07%     
==========================================
  Files         415      418       +3     
  Lines       32134    32199      +65     
==========================================
+ Hits        26763    26842      +79     
+ Misses       4005     4000       -5     
+ Partials     1366     1357       -9     

Files with missing lines	Coverage Δ
internal/xds/xdsdependencymanager/logging.go	100.00% <100.00%> (ø)
internal/xds/resolver/xds_resolver.go	92.44% <85.71%> (+8.11%)	⬆️
internal/grpctest/tlogger.go	74.64% <75.00%> (-0.56%)	⬇️
internal/xds/xdsclient/xdsresource/xdsconfig.go	0.00% <0.00%> (ø)
...xds/xdsdependencymanager/xds_dependency_manager.go	89.47% <89.47%> (ø)
internal/xds/xdsdependencymanager/watch_service.go	73.33% <54.28%> (ø)

... and 26 files with indirect coverage changes

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