CI/CD improvements

[azkrishpy]

Issue #, if available:

N/A

Description of changes:

Adds CI/CD workflows mirroring awslabs/aws-c-common#1250:

• check-abi.yml — ABI compliance check on PRs
• release.yml — manual (workflow_dispatch) release with auto version bump + tag
• block-needs-review.yml — gate merges labeled needs-review
• VERSION file seeded from latest release tag
• CMakeLists.txt: derive target VERSION from VERSION file via aws_get_version()

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.97%. Comparing base (28e4eb3) to head (c58df8f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #824   +/-   ##
=======================================
  Coverage   78.97%   78.97%           
=======================================
  Files          30       30           
  Lines        6534     6534           
=======================================
  Hits         5160     5160           
  Misses       1374     1374           

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