Allow configuring service_name in tracing via EnvoyProxy spec

[sudiptob2]

Fixes #6535

This PR adds support for configuring the service name used in Envoy's tracing configuration through the serviceName field in the EnvoyProxy spec.

Note: The serviceName field is not supported for Zipkin tracing providers. For Zipkin, the service name is always derived from Envoy's --service-cluster flag (typically namespace/name format).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.88%. Comparing base (c3abe4e) to head (99bbfe7).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6568      +/-   ##
==========================================
+ Coverage   70.86%   70.88%   +0.02%     
==========================================
  Files         224      224              
  Lines       38733    38736       +3     
==========================================
+ Hits        27447    27457      +10     
+ Misses       9697     9692       -5     
+ Partials     1589     1587       -2     

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[zirain]

/retest