Add cache built OpenSSL/wolfSSL deps in PR builders to speedup builds in CI

[aidangarske]

Description

Adds a reusable composite action .github/actions/cache-build-deps that caches
the built openssl-install / wolfssl-install (and openssl-source for
patched builds) keyed by resolved commit SHA, so build-wolfprovider.sh skips
the OpenSSL/wolfSSL configure+make on a cache hit. Wired into the normal-PR
from-source builders: cmdline, simple, smoke-test, seed-src,
fips-ready.

Pattern mirrors the existing multi-compiler.yml cache (resolve-ref -> SHA ->
actions/cache): a stable tag resolves to a fixed SHA (cached across runs);
master resolves to current HEAD (rebuilt only when upstream moves). The unit
under test (wolfprov-install) is never cached.

Measured effect (verified on this PR: cold run 1 -> warm run 2)

Workflow	cold avg (from scratch)	warm avg (cache hit)	speedup
cmdline	283 s	52 s	5.4x
simple (incl. replace-default rows)	~262 s	41 s	6.4x
smoke-test	308 s	49 s	6.3x
seed-src	298 s	38 s	7.8x
fips-ready	~300 s	44 s	~7x

Per heavy config the from-scratch dep build is ~5:30-5:50; on a warm cache the
build step drops to ~30-50 s (about 5 min saved per cached job). All builders
passed on both the cold and warm runs.

Validation

• Warm-run log confirms master rows hit on the resolved HEAD SHA
  ("Cache hit ... Cache restored successfully"): master is reused when the commit
  is unchanged and rebuilds when it moves; stable tags hit unconditionally.
• Replace-default / FIPS-baseline rows (simple.yml) also cache openssl-source
  so the source-reading mismatch checks pass on a hit.
• Variant token encodes every build-config dimension (compiler/debug/
  replace-default/seed-src/fips) so no wrong-config cache hit.
• FIPS bundle cached by stable version; wget only runs on a cache miss.