Bumps [sigstore/cosign-installer](https://github.com/sigstore/cosign-installer) from 3.9.0 to 3.9.1.
- [Release notes](https://github.com/sigstore/cosign-installer/releases)
- [Commits](sigstore/cosign-installer@fb28c2b...398d4b0)

---
updated-dependencies:
- dependency-name: sigstore/cosign-installer
  dependency-version: 3.9.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

It's reasonable common for the image pushing step to fail in CI due to
transient network issues, so it makes sense to expose the `--retry-push`
and `--retry-count` options in the GitHub action. This adds a
`retry_push_count` option to the action that defaults to 0, and if set
to be nonzero, it enables `--retry-push` and passes the retry count to
the CLI.

I also did a bit of minor cleanup of the action:
* Updated actions/checkout to v5.0.0.
* Added `persist-credentials: false` to actions/checkout for security,
  per Zizmor recommendation.
* Converted direct template expansions (which are potentially
  vulnerable to code injection attacks) into environment variables.
* Quoted shell variables to prevent unintended shell splitting.

Signed-off-by: Daniel Hast <[email protected]>

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>