perf(gRPC): reduce object allocations on the gRPC client side for unified cancel scenarios

[DMwangnima]

What type of PR is this?

perf

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo

(Optional) Translate the PR title into Chinese.

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:

• Split closeStream into casStreamDone and doCloseStream so that Tick can skip already-closed streams before constructing status/error objects.
• Introduce contextStatusAndErr returning reused singleton status and error for context.Canceled / context.DeadlineExceeded to avoid per-stream allocation.
• Guard shared status via Stream.reuseStatus flag and lazy deep copy in Stream.Status().
• Remove unused eosReceived parameter from client-side closeStream.
• Add reuseStatus defense tests and closeStreamTask
• Tick benchmarks.

zh(optional):

(Optional) Which issue(s) this PR fixes:

(optional) The PR that updates user documentation:

[codecov]

Codecov Report

❌ Patch coverage is 82.05128% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.63%. Comparing base (bfa27f3) to head (779b183).
⚠️ Report is 45 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/remote/trans/nphttp2/grpc/http2_client.go	70.83%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1950      +/-   ##
==========================================
+ Coverage   61.37%   62.63%   +1.25%     
==========================================
  Files         388      393       +5     
  Lines       35063    30106    -4957     
==========================================
- Hits        21521    18857    -2664     
+ Misses      12247     9952    -2295     
- Partials     1295     1297       +2     

Flag	Coverage Δ
integration	51.63% <56.41%> (+1.13%)	⬆️
unit	53.04% <79.48%> (+1.40%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.