Remove Java formatting from build task in CI (#3507)

This saves time in CI spent performing the same source-level checks in
every build job. Checkstyle, PMD, and Spotless are now run once in the
"Lint and Format" job.

The -PskipPMD flag was replaced with a -PskipJavaFormat flag that
disables Checkstyle, PMD, and Spotless.

.github/workflows/lint-format.yml

@@ -69,3 +69,23 @@ jobs:
         run: wpiformat -list-changed-files
       - name: Run clang-tidy
         run: wpiformat -clang 12 -no-format -tidy-changed -compile-commands=build-cmake
+  spotless:
+    name: "Spotless"
+    runs-on: ubuntu-latest
+    container: wpilib/ubuntu-base:18.04
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Run spotless
+        run: ./gradlew spotlessCheck
+  javaformat:
+    name: "Checkstyle and PMD"
+    runs-on: ubuntu-latest
+    container: wpilib/ubuntu-base:18.04
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Run Java format
+        run: ./gradlew javaFormat