feat: cluster stat name

[guydc]

What type of PR is this?

What this PR does / why we need it:
Add support for determining cluster stat names in EnvoyProxy.

• Supported Clusters: HTTPRoute and GRPCRoute
• Supported Formatters: %ROUTE_KIND%, %ROUTE_NAME%, %ROUTE_NAMESPACE%, %ROUTE_RULE_NAME%, %ROUTE_RULE_NUMBER%, %BACKEND_REFS%.

Which issue(s) this PR fixes:

Relates #4717

Release Notes: Yes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.57%. Comparing base (598c813) to head (8f59cd5).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5898      +/-   ##
==========================================
+ Coverage   70.49%   70.57%   +0.07%     
==========================================
  Files         220      220              
  Lines       36639    36703      +64     
==========================================
+ Hits        25830    25904      +74     
+ Misses       9281     9273       -8     
+ Partials     1528     1526       -2     

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[DerrickMartinez]

Thanks for doing this. What is the latest with this PR?

[guydc]

@DerrickMartinez - Post the 1.4 release (hopefully this week), maintainers should have more bandwidth to push this forward in the 1.5 scope. Thanks for expressing interest, this helps prioritize the issue.

[arkodg]

should we split this up into ROUTE_NAME and ROUTE_NAMESPACE ?

[arkodg]

or ROUTE_RULE_NAME ?

[arkodg]

Suggested change

	// Only HTTPRoute and GRPCRoute clusters are currently supported.
	// Only xDS Clusters created by HTTPRoute and GRPCRoute resources are currently supported.

[arkodg]

can we add an example of this here ?

[arkodg]

LGTM thanks, one comment around the CEL test which is removing the older one

[arkodg]

LGTM.thanks !