Add a kms-tests.yml workflow that runs on changes to KMS/SSE code with
two jobs:
1. KMS provider tests: starts OpenBao via Docker, runs Go integration
tests in test/kms/ against a real KMS backend
2. S3 KMS e2e tests: starts OpenBao + weed mini built from source, runs
test_s3_kms.sh which covers bucket-default SSE-KMS upload/download
(the exact scenario from #8776)
Supporting changes:
- test/kms/Makefile: add CI targets (test-provider-ci, test-s3-kms-ci)
that manage OpenBao via plain Docker and run weed from source
- test/kms/s3-config-openbao-template.json: S3 config template with
OpenBao KMS provider for weed mini