cherry-pick #7660 to v1.66.x branch

[arjan-bal]

Fixes: #7641
Original PR: #7660

RELEASE NOTES:

• transport: Fix a bug causing stream failures due to miscalculation of the flow control window in both clients and servers.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.78%. Comparing base (a75eb1e) to head (d53bc9a).
Report is 1 commits behind head on v1.66.x.

Additional details and impacted files

@@             Coverage Diff             @@
##           v1.66.x    #7668      +/-   ##
===========================================
- Coverage    81.90%   81.78%   -0.12%     
===========================================
  Files          361      361              
  Lines        27858    27858              
===========================================
- Hits         22816    22783      -33     
- Misses        3851     3868      +17     
- Partials      1191     1207      +16     

Files with missing lines	Coverage Δ
internal/transport/transport.go	92.69% <100.00%> (+1.53%)	⬆️

... and 21 files with indirect coverage changes

[easwars]

@dfawley : Do we want to cherrypick this into 1.66? We already have 1.67 out and we are cherrypicking this into 1.67. There is about a month to go for 1.68 though.

The reason I'm asking is if somebody is bitten by this bug in 1.66, what is the value of having another patch release in 1.66 to upgrade to over upgrading to 1.67.

[dfawley]

Yes, we should do a patch release of 1.66 with this, too, since it's a pretty serious issue..