Extract github actions for interesting rust toolchain versions

Extract a github action to reduce the number of references to our MSRV and
stable (to be pinned in the next commit).

While at it, use the MSRV for macOS builds; this means that we'll be less
like accidentally to break the macOS build when bumping the MSRV.  I don't
think there is a reason for using 1.73 specifically, other than "it's the
highest we can use on old macOS", so using an even older one should be fine.

.github/actions/rust-toolchain@oldest-supported/action.yml

@@ -0,0 +1,22 @@
+name: Oldest Supported Rust Toolchain
+
+on:
+  workflow_call:
+    inputs:
+      targets:
+        description: Comma-separated list of target triples to install for this toolchain
+        required: false
+      components:
+        description: Comma-separated list of components to be additionally installed
+        required: false
+
+permissions:
+  contents: read
+
+runs:
+  using: "composite"
+  steps:
+    - uses: dtolnay/rust-toolchain@1.70
+      with:
+        targets: ${{ inputs.targets }}
+        components: ${{ inputs.components}}

.github/actions/rust-toolchain@stable/action.yml

@@ -0,0 +1,22 @@
+name: Stable Rust Toolchain
+
+on:
+  workflow_call:
+    inputs:
+      targets:
+        description: Comma-separated list of target triples to install for this toolchain
+        required: false
+      components:
+        description: Comma-separated list of components to be additionally installed
+        required: false
+
+permissions:
+  contents: read
+
+runs:
+  using: "composite"
+  steps:
+    - uses: dtolnay/rust-toolchain@stable
+      with:
+        targets: ${{ inputs.targets }}
+        components: ${{ inputs.components }}

.github/workflows/mac_codesign.yml

@@ -9,12 +9,12 @@ jobs:
     environment: macos-codesign
     steps:
       - uses: actions/checkout@v4
-      - name: Install Rust 1.73.0
-        uses: dtolnay/rust-toolchain@1.73.0
+      - name: Install Rust
+        uses: ./.github/actions/rust-toolchain@oldest-supported
         with:
           targets: x86_64-apple-darwin
       - name: Install Rust Stable
-        uses: dtolnay/rust-toolchain@stable
+        uses: ./.github/actions/rust-toolchain@stable
         with:
           targets: aarch64-apple-darwin
       - name: build-and-codesign

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@1.70
+    - uses: ./.github/actions/rust-toolchain@oldest-supported
     - name: Install deps
       run: |
         sudo apt install gettext libpcre2-dev python3-pexpect python3-sphinx tmux
@@ -47,7 +47,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@1.70
+    - uses: ./.github/actions/rust-toolchain@oldest-supported
       with:
         targets: "i586-unknown-linux-gnu" # rust-toolchain wants this comma-separated
     - name: Install deps
@@ -128,7 +128,7 @@ jobs:
   #
   #   steps:
   #   - uses: actions/checkout@v4
-  #   - uses: dtolnay/rust-toolchain@1.70
+  #   - uses: ./.github/actions/rust-toolchain@oldest-supported
   #   - name: Install deps
   #     run: |
   #       sudo apt install gettext libpcre2-dev python3-pexpect tmux
@@ -156,7 +156,7 @@ jobs:
       CARGO_NET_GIT_FETCH_WITH_CLI: true
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@1.70
+    - uses: ./.github/actions/rust-toolchain@oldest-supported
     - name: Install deps
       run: |
         # --break-system-packages because homebrew has now declared itself "externally managed".

.github/workflows/rust_checks.yml

@@ -11,7 +11,9 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: ./.github/actions/rust-toolchain@stable
+      with:
+        components: rustfmt
     - name: cargo fmt
       run: cargo fmt --check
 
@@ -20,7 +22,9 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: ./.github/actions/rust-toolchain@stable
+      with:
+        components: clippy
     - name: Install deps
       run: |
         sudo apt install gettext libpcre2-dev
@@ -37,18 +41,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: ./.github/actions/rust-toolchain@stable
     - name: cargo doc
       run: |
         RUSTDOCFLAGS='-D warnings' cargo doc --workspace
     - name: cargo doctest
       run: |
         cargo test --doc --workspace
-
-  # Disabling for now because it also checks "advisories",
-  # making CI fail for reasons unrelated to the patch
-  # cargo-deny:
-  #   runs-on: ubuntu-latest
-  #   steps:
-  #   - uses: actions/checkout@v3
-  #   - uses: EmbarkStudios/cargo-deny-action@v1

.github/workflows/staticbuild.yml

@@ -16,7 +16,7 @@ jobs:
       contents: read
 
     steps:
-    - uses: dtolnay/rust-toolchain@1.70
+    - uses: ./.github/actions/rust-toolchain@oldest-supported
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
@@ -51,7 +51,7 @@ jobs:
       contents: read
 
     steps:
-    - uses: dtolnay/rust-toolchain@1.70
+    - uses: ./.github/actions/rust-toolchain@oldest-supported
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0