Pin our GitHub Actions dependencies (#18255)

After the [recent supply chain attack](https://www.wiz.io/blog/new-github-action-supply-chain-attack-reviewdog-action-setup)
in `tj-actions/changed-files` and actions based on it, it's become clear
that relying on git tags to pin our dependencies is not enough (as tags
can simply be replaced). Therefore we need to switch to hashes.

Dependabot should continue to update these dependencies for us.

Best reviewed commit-by-commit. Though if CI passes, we're *probably*
fine.

.github/workflows/fix_lint.yaml

@@ -13,19 +13,19 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
       - name: Install Rust
-        uses: dtolnay/rust-toolchain@master
+        uses: dtolnay/rust-toolchain@56f84321dbccf38fb67ce29ab63e4754056677e0 # master (rust 1.85.1)
         with:
           # We use nightly so that `fmt` correctly groups together imports, and
           # clippy correctly fixes up the benchmarks.
           toolchain: nightly-2022-12-01
           components: clippy, rustfmt
-      - uses: Swatinem/rust-cache@v2
+      - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
 
       - name: Setup Poetry
-        uses: matrix-org/setup-python-poetry@v1
+        uses: matrix-org/setup-python-poetry@4421c92b6223f03ae55560e29aa8ebd39cf6314a # v1.2.4
         with:
           install-project: "false"
 
@@ -43,6 +43,6 @@ jobs:
       - run: cargo fmt
         continue-on-error: true
 
-      - uses: stefanzweifel/git-auto-commit-action@v5
+      - uses: stefanzweifel/git-auto-commit-action@e348103e9026cc0eee72ae06630dbe30c8bf7a79 # v5.1.0
         with:
           commit_message: "Attempt to fix linting"