CI: github: test AWS-LC 3.x and 4.x LTS branches

CI: github: test AWS-LC 3.x and 4.x LTS branches

Add the fips-2024-09-27 (3.x) and fips-2025-09-12-lts (4.x) AWS-LC
branches to the VTest matrix for GCC and Clang, including QUIC support.

Resolve each branch head to a commit SHA when generating the matrix
and download the corresponding immutable archive in build-ssl.sh.
Read the AWS-LC version from that commit's header to display readable
job names such as ssl=aws_lc=4.2.0+37341efe.

Generate the SSL cache key from both the job name and SSL source,
retaining the full commit SHA even though the display uses only eight
characters. Builds are reused until the branch advances, and distinct
commits cannot share a cache entry because of a short SHA collision.

Validated branch resolution and version extraction against GitHub,
readable GCC and Clang jobs in development and stable matrices, commit
and tag archive URLs, cache reuse, shell syntax, and git diff --check.