ci: Use nextest --retries in CI (#39817)

Follow-up to #39812, using nextests builtin retry feature to rerun flaky
unit-tests.
This also adds a per-test timeout, replacing the global timeout set for
the retry action. We could also add a global timeout for nextest tests,
but per-test timeouts should be sufficient and noticably speedup CI when
individual unit tests get stuck.

Testing: [mach
try](https://github.com/servo/servo/actions/runs/18519094535) running
the unit-tests with retries in CI.

---------

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

.config/nextest.toml

@@ -0,0 +1,3 @@
+[profile.default]
+# Print a slow warning after period, terminate unit-test after 4x period.
+slow-timeout = { period = "5s", terminate-after = 4 }

.github/workflows/linux.yml

@@ -188,6 +188,9 @@ jobs:
       - name: Change Mirror Priorities
         if: ${{ runner.environment != 'self-hosted' }}
         uses: ./.github/actions/apt-mirrors
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: nextest
       - name: Bootstrap dependencies
         if: ${{ runner.environment != 'self-hosted' }}
         timeout-minutes: 10
@@ -209,17 +212,11 @@ jobs:
         run: xvfb-run ./mach smoketest --${{ inputs.profile  }}
       - name: Script tests
         run: ./mach test-scripts
-      - name: Install cargo nextest
-        uses: taiki-e/install-action@v2
-        with:
-          tool: nextest
       - name: Unit tests
         if: ${{ inputs.unit-tests }}
-        uses: nick-fields/retry@v3
-        with:
-          timeout_minutes: 20
-          max_attempts: 2 # https://github.com/servo/servo/issues/30683
-          command: ./mach test-unit --${{ inputs.profile }}
+        env:
+          NEXTEST_RETRIES: 2 # https://github.com/servo/servo/issues/30683
+        run: ./mach test-unit --${{ inputs.profile }}
       - name: Devtools tests
         if: ${{ inputs.unit-tests }}
         run: ./mach test-devtools --${{ inputs.profile }}

.github/workflows/mac.yml

@@ -168,6 +168,10 @@ jobs:
       - name: Install crown
         run: cargo install --path support/crown
 
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: nextest
+
       - if: runner.environment != 'self-hosted'
         name: Bootstrap
         run: |
@@ -185,17 +189,11 @@ jobs:
           command: ./mach smoketest --${{ inputs.profile }}
       - name: Script tests
         run: ./mach test-scripts
-      - name: Install cargo nextest
-        uses: taiki-e/install-action@v2
-        with:
-          tool: nextest
       - name: Unit tests
         if: ${{ inputs.unit-tests }}
-        uses: nick-fields/retry@v3
-        with:
-          timeout_minutes: 40 # https://github.com/servo/servo/issues/30275
-          max_attempts: 3 # https://github.com/servo/servo/issues/30683
-          command: ./mach test-unit --${{ inputs.profile }}
+        env:
+          NEXTEST_RETRIES: 3 # https://github.com/servo/servo/issues/30683
+        run: ./mach test-unit --${{ inputs.profile }}
       - name: Devtools tests
         if: ${{ inputs.unit-tests }}
         run: ./mach test-devtools --${{ inputs.profile }}

.github/workflows/windows.yml

@@ -180,7 +180,6 @@ jobs:
       # commit we are building uses a different rustc version.
       - name: Install crown
         run: cargo install --path support/crown --force
-
       - name: Debug logging for incremental builds
         if: ${{ runner.environment == 'self-hosted' }}
         run: |
@@ -209,11 +208,9 @@ jobs:
         run: cargo install cargo-nextest --locked
       - name: Unit tests
         if: ${{ inputs.unit-tests }}
-        uses: nick-fields/retry@v3
-        with:
-          timeout_minutes: 30
-          max_attempts: 3 # https://github.com/servo/servo/issues/30683
-          command: .\mach test-unit --${{ inputs.profile }} -- -- --test-threads=1
+        env:
+          NEXTEST_RETRIES: 3 # https://github.com/servo/servo/issues/30683
+        run: ./mach test-unit --${{ inputs.profile }}
       - name: Devtools tests
         if: ${{ inputs.unit-tests }}
         run: .\mach test-devtools --${{ inputs.profile }}