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 74.49%. Comparing base (bce67e0) to head (b409481).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #256   +/-   ##
=======================================
  Coverage   74.49%   74.49%           
=======================================
  Files          18       18           
  Lines        2341     2341           
=======================================
  Hits         1744     1744           
  Misses        597      597           

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