fix: implement comparable interface for ir.Xds to skip unnecessary updates

[dboslee]

What this PR does / why we need it:
This change implements the comparable interface used by watchable to sort ir.Xds listeners when checking for differences. This reduces the number of xds updates that get pushed to envoy during re-syncs of k8s resources.

Which issue(s) this PR fixes:
fixes #1634

[codecov]

Codecov Report

Merging #1795 (a1bdeb2) into main (677cf03) will increase coverage by 0.05%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##             main    #1795      +/-   ##
==========================================
+ Coverage   64.95%   65.00%   +0.05%     
==========================================
  Files          84       84              
  Lines       12209    12230      +21     
==========================================
+ Hits         7930     7950      +20     
+ Misses       3773     3768       -5     
- Partials      506      512       +6     

Files Changed	Coverage Δ
internal/ir/xds.go	72.56% <85.71%> (+0.89%)	⬆️

... and 3 files with indirect coverage changes

[arkodg]

there's a lint error

Error: ST1016: methods on the same type should have the same receiver name (seen 1x "x1", 6x "x") (stylecheck)

probably can be recreated by running make lint locally

[arkodg]

LGTM thanks for adding this
would also be great to see if watchable is actually leveraging this Equal method with a test in
https://github.com/envoyproxy/gateway/blob/main/internal/message/watchutil_test.go

[dboslee]

LGTM thanks for adding this would also be great to see if watchable is actually leveraging this Equal method with a test in https://github.com/envoyproxy/gateway/blob/main/internal/message/watchutil_test.go

Sure thing. I will add a test for this.

[arkodg]

awesome, thanks !

[AliceProxy]

Looks good, thanks for contributing 🚀