ci: Convert remaining jobs to GitHub actions

.github/workflows/msrv.yml

@@ -0,0 +1,31 @@
+name: Rust 1.45
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+      - name: Install rust 1.45 toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: '1.45'
+      # Used to compile xtask
+      - name: Install rust stable toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - name: Run checks
+        uses: actions-rs/cargo@v1
+        with:
+          command: run
+          args: -p xtask --no-default-features ci msrv

.github/workflows/nightly.yml

@@ -0,0 +1,25 @@
+name: Rust nightly
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v2
+      - name: Install rust nightly toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+      - name: Run checks
+        uses: actions-rs/cargo@v1
+        with:
+          command: run
+          args: -p xtask --no-default-features ci nightly

.github/workflows/stable.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - name: Checkout repo
         uses: actions/checkout@v2
-      - name: Install stable rust toolchain
+      - name: Install rust stable toolchain
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal