xds: refactor server-side HTTP filter processing

[easwars]

While working on xDS HTTP filter state retention changes required for A83 and A86 in #8745, I realized that the current implementation of HTTP filters on the server-side does not lend itself well to the changes we want to make to support filter state retention. The crux of the problem in the current implementation is as follows:

• The xdsresource package builds a FilterChainManager type that does the following:
  • Keeps track of the list of Route Configuration resources to be requested based on the HTTP filters configured on the Listener resource
  • Updates the interceptors on the different filter chains based on Route Configuration resource updates (that contain filter config overrides)
  • Maintaining runtime state in a type that is supposed to represent a configuration blob seems to have been a wrong implementation choice
• Everytime a Listener resource update is received, the xdsresource package builds a brand new FilterChainManager
  • This means that we cannot retain filter state across resource updates

This PR makes the following changes:

• Changes the layout of the ListenerUpdate struct to clearly separate client-side and server-side fields
  • Also groups information that is shared across client and server listener types into a logical struct
  • The ListenerUpdate will only contain information directly sources from the listener proto
• The xDS server implementation will build the runtime representation of the filter chains using the configuration update provided by the xdsresource package
  • This would move the responsibility of updating the interceptors on the filter chain to the xDS server, which is the correct place to be doing such a thing
  • This would make it possible for the xDS server implementation to retain filter state across listener resource updates

RELEASE NOTES: none

[codecov]

Codecov Report

❌ Patch coverage is 92.59259% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.31%. Comparing base (b7b1cce) to head (f313996).

Files with missing lines	Patch %	Lines
internal/xds/server/filter_chain_manager.go	90.78%	7 Missing and 7 partials ⚠️
internal/xds/server/routing.go	85.18%	7 Missing and 5 partials ⚠️
...nternal/xds/xdsclient/xdsresource/unmarshal_lds.go	97.89%	3 Missing and 1 partial ⚠️
...ds/xdsclient/xdsresource/listener_resource_type.go	85.71%	1 Missing and 1 partial ⚠️
internal/xds/xdsdepmgr/xds_dependency_manager.go	66.66%	1 Missing and 1 partial ⚠️
internal/xds/resolver/xds_resolver.go	66.66%	1 Missing ⚠️
internal/xds/server/listener_wrapper.go	96.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8878      +/-   ##
==========================================
+ Coverage   83.20%   83.31%   +0.10%     
==========================================
  Files         414      416       +2     
  Lines       32751    32812      +61     
==========================================
+ Hits        27250    27336      +86     
+ Misses       4084     4069      -15     
+ Partials     1417     1407      -10     

Files with missing lines	Coverage Δ
internal/xds/server/conn_wrapper.go	76.27% <100.00%> (-0.78%)	⬇️
internal/xds/xdsclient/xdsresource/filter_chain.go	92.15% <100.00%> (-1.77%)	⬇️
internal/xds/xdsclient/xdsresource/matcher.go	60.68% <ø> (-3.50%)	⬇️
xds/server.go	82.55% <100.00%> (+1.10%)	⬆️
internal/xds/resolver/xds_resolver.go	88.76% <66.66%> (ø)
internal/xds/server/listener_wrapper.go	79.41% <96.66%> (+0.12%)	⬆️
...ds/xdsclient/xdsresource/listener_resource_type.go	93.65% <85.71%> (-2.51%)	⬇️
internal/xds/xdsdepmgr/xds_dependency_manager.go	80.69% <66.66%> (+0.55%)	⬆️
...nternal/xds/xdsclient/xdsresource/unmarshal_lds.go	93.49% <97.89%> (+5.02%)	⬆️
internal/xds/server/routing.go	85.18% <85.18%> (ø)
... and 1 more

... and 26 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.