cherry-pick: transport: add timeout for writing GOAWAY on http2Client.Close() #7371

[aranjans]

fixes #7314

Problem
In gRPC 1.64, we released a #7015 "Send GOAWAY to server on Client Transport Shutdown", post which in case of network hang when we are not able to write GOAWAY frame from client, closing connections will take a very long time.

What does this PR fix
This PR fixes this issue by having a timeout for loopyWriter to write GOAWAY so that http2Client.Close() doesn't wait for too long.

RELEASE NOTES:

• client: prevent hanging during ClientConn.Close() when the network is unreachable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.86%. Comparing base (63853fd) to head (55bd4bd).
Report is 1 commits behind head on v1.66.x.

Additional details and impacted files

@@             Coverage Diff             @@
##           v1.66.x    #7540      +/-   ##
===========================================
- Coverage    82.05%   81.86%   -0.20%     
===========================================
  Files          360      360              
  Lines        27533    27539       +6     
===========================================
- Hits         22593    22544      -49     
- Misses        3762     3798      +36     
- Partials      1178     1197      +19     

Files	Coverage Δ
internal/transport/http2_client.go	91.90% <100.00%> (+0.04%)	⬆️

... and 18 files with indirect coverage changes

[arvindbr8]

The relnotes should talk more about the bug along with what the fix was. Users would be interested to know if they might be impacted by the bug.

[aranjans]

@arvindbr8 updated the description

[arvindbr8]

Also feel free to update the relnotes for the release itself. Now when i think about it, the relnotes in the description here does not get picked up

[dfawley]

No user will understand this release note, either; it's written more like it's for a gRPC developer. The release notes should talk about the user-visible problem is being fixed. "client: prevent hanging during ClientConn.Close() when the network is unreachable" or something like that.

[arvindbr8]

cc: @aranjans

[aranjans]

Acknowledged, updated the release note.