transport: handle 1xx HTTP status HEADERS at the client side

[vinothkumarr227]

Fixes: #8485

RELEASE NOTES:

• client: Ignore http headers with status 1xx and END_STREAM flag unset.
• client: Fail RPCs with status INTERNAL instead of UNKNOWN on receiving http headers with status 1xx and END_STREAM flag set.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.94%. Comparing base (9ac0ec8) to head (7dac9dd).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8518      +/-   ##
==========================================
+ Coverage   81.82%   81.94%   +0.12%     
==========================================
  Files         413      412       -1     
  Lines       40518    40469      -49     
==========================================
+ Hits        33153    33163      +10     
+ Misses       5989     5915      -74     
- Partials     1376     1391      +15     

Files with missing lines	Coverage Δ
internal/transport/http2_client.go	91.84% <100.00%> (+0.02%)	⬆️

... and 238 files with indirect coverage changes

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[arjan-bal]

2 small changes, otherwise LGTM. Please address them before I add a second reviewer.