ci: add daily test workflow for slower tests

This commit adds a `daily-tests.yml` GitHub actions workflow. It's
triggered by a cron schedule to run once a day. Presently it only runs
opt-in ignored tests but in the future we can extend it with other
slow running tasks we don't want to have bog down our main CI
process.

Author: cpu

.github/workflows/daily-tests.yml

@@ -0,0 +1,46 @@
+name: daily-tests
+
+permissions:
+  contents: read
+
+on:
+  schedule:
+    # We run these tests on a daily basis (at a time slightly offset from the
+    # top of the hour), as their runtime is either too long for the usual per-PR
+    # CI, or because they rely on external 3rd party services that can be flaky.
+    - cron: '15 18 * * *'
+
+jobs:
+  ignored:
+    # Run slower tests we make opt-in with the #[ignore] annotation.
+    name: Ignored tests
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        # test a bunch of toolchains on ubuntu
+        rust:
+          - stable
+          - beta
+          - nightly
+        os: [ubuntu-20.04]
+        # but only stable on macos/windows (slower platforms)
+        include:
+          - os: macos-latest
+            rust: stable
+          - os: windows-latest
+            rust: stable
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: Install ${{ matrix.rust }} toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+
+      - name: Run ignored tests
+        run: cargo test -- --ignored
+        env:
+          RUST_BACKTRACE: 1