otelgrpc: add server.address and server.port

[dashpole]

Part of #6608 (leaving it open because this isn't fixing server metrics).

Adds server.address and server.port attributes to otelgrpc client and server metrics to match what is in the latest semantic conventions.

This also fixes an issue where server spans were using peer.FromContext(ctx) as the server's IP and port. It is actually the client's IP and Port.

For client + server spans and for client metrics, it has the same requirement level:

server.address Conditionally Required If available.

server.port Conditionally Required if applicable and if server.address is set.

For server metrics, it is Opt-In, so it is left as a TODO to add those attributes:

server.address Opt-In

server.port Opt-In

Detailed description is the same everywhere:

[5] server.address: May contain a DNS name, an endpoint and path in the service registry, local socket name or an IP address. Semantic conventions for individual RPC systems SHOULD document how to populate this attribute. When address is an IP address, instrumentations SHOULD NOT do a reverse DNS lookup to obtain a DNS name and SHOULD set server.address to the provided IP address.

[6] server.port: When observed from the client side, and when communicating through an intermediary, server.port SHOULD represent the server port behind any intermediaries, for example proxies, if it’s available.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.2%. Comparing base (1676912) to head (4f4b149).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8723   +/-   ##
=====================================
  Coverage   82.2%   82.2%           
=====================================
  Files        183     183           
  Lines      13812   13819    +7     
=====================================
+ Hits       11354   11361    +7     
  Misses      2054    2054           
  Partials     404     404           

Files with missing lines	Coverage Δ
...n/google.golang.org/grpc/otelgrpc/stats_handler.go	98.5% <100.0%> (+<0.1%)	⬆️

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