cherry-pick #7660 to v1.67.x branch

[arjan-bal]

Addresses: #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 81.95%. Comparing base (02bbb65) to head (7398679).
Report is 1 commits behind head on v1.67.x.

Additional details and impacted files

@@             Coverage Diff             @@
##           v1.67.x    #7667      +/-   ##
===========================================
+ Coverage    81.93%   81.95%   +0.01%     
===========================================
  Files          361      361              
  Lines        27813    27813              
===========================================
+ Hits         22788    22793       +5     
+ Misses        3838     3833       -5     
  Partials      1187     1187              

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

... and 18 files with indirect coverage changes