Bump version and changelog for v5.9.12

[DrJosh9000]

v5.9.12 (2024-12-17)

Full Changelog

Release process changes

• Update release process to assume new IAM roles via OIDC #352 (@yob)
• Simplify docker release script #347 (@yob)

Dependency updates

• Group container image bumps into single PR #356 (@DrJosh9000)
• build(deps): bump golang.org/x/crypto from 0.28.0 to 0.31.0 #358 (@dependabot[bot])
• build(deps): bump google.golang.org/protobuf from 1.35.2 to 1.36.0 #357 (@dependabot[bot])
• build(deps): bump docker/library/golang from 574185e to 7003184 #353 (@dependabot[bot])
• build(deps): bump docker/library/golang from 6c5c959 to 6c5c959 in /.buildkite #354 (@dependabot[bot])
• build(deps): bump cloud.google.com/go/monitoring from 1.21.2 to 1.22.0 #348 (@dependabot[bot])
• build(deps): bump docker/library/alpine from 3.20.3 to 3.21.0 #350 (@dependabot[bot])
• build(deps): bump docker/library/golang from 1.23.3 to 1.23.4 #349 (@dependabot[bot])
• build(deps): bump docker/library/golang from 1.23.3 to 1.23.4 in /.buildkite #351 (@dependabot[bot])

[yob]

Time to see what I broke in the release pipeline 👍