Handle global max blocks semaphore properly

[ashmeenkaur]

Description

we are creating at least 1 block for each inode even if we are out of global max blocks (tracked by globalMaxBlocksSem semaphore), but at the time of releasing blocks we are not checking if the semaphore was acquired. This leads to panic("semaphore: released more than held").
This PR fixes this panic by always creating the 1st block without checking globalMaxBlocks and now we don't release the semaphore for last block in blockpool.

Link to the issue in case of a bug fix.

b/385057665

Testing details

1. Manual - NA
2. Unit tests - Added
3. Integration tests - NA

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.10%. Comparing base (7a13c4a) to head (ad084e0).
Report is 36 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2860      +/-   ##
==========================================
- Coverage   76.15%   76.10%   -0.05%     
==========================================
  Files         118      118              
  Lines       16596    16604       +8     
==========================================
- Hits        12639    12637       -2     
- Misses       3425     3433       +8     
- Partials      532      534       +2     

Flag	Coverage Δ
unittests	76.10% <100.00%> (-0.05%)	⬇️

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.