S3CSI-29: Add tests suite for prefix, region and read-only mountoptions

[anurag4DSB]

Added tests for volume level options for specifying --region (overrides driver level region), --prefix (mounts bucket using a specific prefix), and --read-only (for read only filesystem)

The test cases added are either important for us or we have changed the related options behaviour so we need to test.
The rest of the scenarios are testing in the upstream mountpoint-s3

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.83%. Comparing base (7fd9fdf) to head (da692b6).
Report is 8 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

see 1 file with indirect coverage changes

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   64.78%   64.83%   +0.04%     
==========================================
  Files          37       37              
  Lines        2090     2090              
==========================================
+ Hits         1354     1355       +1     
+ Misses        660      659       -1     
  Partials       76       76