[build] Harden CI/CD pipeline (#15387)

* NOTE: the release workflows' new handling of secrets
  may be a breaking change for forks that are using any secrets
  other than GPG_SIGNING_KEY or ARCHIVE_REPO_TOKEN.

  Previously, the release workflow would try to resolve a token
  secret name based on the `target` or `source` input,
  e.g. NIGHTLY_ARCHIVE_REPO_TOKEN or CUSTOM_ARCHIVE_REPO_TOKEN,
  and then fall back to using the ARCHIVE_REPO_TOKEN secret if the
  resolved token secret name was not found in the repository.

  This behavior has been replaced by the release workflow
  always using the ARCHIVE_REPO_TOKEN secret as the token
  for publishing releases to any external archive repository.

* Add zizmor CI job for auditing workflows

* Pin all actions to commit hashes instead of symbolic references

* Explicitly set GITHUB_TOKEN permissions at the job level

* Use actions/checkout with `persist-credentials: false` whenever possible

* Remove/replace template expansions in workflow scripts

* Remove all usage of actions/cache from build/release workflows

* Remove the cache-warmer.yml workflow

* Remove the unused download.yml workflow

* Set concurrency limits for any workflows that are triggered by PRs

* Avoid loading the entire secrets context

* Replace usage of `secrets: inherit` with explicit `secrets:` blocks

* Pin all external docker images to hash that are used by the build workflow

* Explicitly set `shell: bash` for some steps to avoid pwsh or set pipefail

* Ensure any pwsh steps will fail on non-zero exit codes

Authored by: bashonly

.github/workflows/core.yml

@@ -57,12 +57,12 @@ jobs:
         - os: windows-latest
           python-version: pypy-3.11
     steps:
-    - uses: actions/checkout@v6
+    - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8  # v6.0.1
       with:
         fetch-depth: 0
         persist-credentials: false
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v6
+      uses: actions/setup-python@83679a892e2d95755f2dac6acb0bfd1e9ac5d548  # v6.1.0
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install test requirements