The packer-built almalinux9-gobuilder image is being retired. Switch
test and pre-commit steps to artifactapi docker-internal/gobuilder
0.1.2-alma9, which trusts the estate CA and ships go-cache-plugin
baked in on PATH.
- Point test/pre-commit steps at the new image
- Drop the curl/sha256sum bootstrap for go-cache-plugin; set
GOCACHEPROG directly as a static env var since the binary is
always present now
- Best-effort S3 cache behaviour is unchanged: verified go build/test
still succeed with unreachable/invalid S3 credentials, since the
plugin itself degrades to cache misses at runtime
unkin-agent