Fix cache warmer: Linux-only, OS-agnostic cache key (#1380)

## Summary
- Fix cache warmer Windows failure: drop Windows from matrix (bash not
available on Databricks protected Windows runners)
- Make cache key OS-agnostic: Maven JARs/POMs are platform-independent,
one cache entry serves both Linux and Windows
- Cache key: `maven-deps-{hash(pom.xml)}` (was `{os}-maven-deps-{hash}`)
- Includes all changes from #1369 (runner revert + forked PR caching
infrastructure)

## Changes
- `.github/actions/setup-maven/action.yml` -- Reusable composite action
for fork detection + JFrog/cache setup
- `.github/workflows/warmMavenCache.yml` -- Cache warmer workflow
(Linux-only)
- `.github/workflows/prCheck.yml`, `prIntegrationTests.yml`,
`coverageReport.yml`, `prCheckJDK8.yml`, `concurrencyExecutionTests.yml`
-- Use composite action

## Design doc

https://docs.google.com/document/d/17g9QN6LwbaiELLvrbClT_yKUfKuOHR5fYSdMDMhXd80/edit

## Test plan
- [ ] Trigger cache warmer on main after merge -- should succeed on
Linux
- [ ] Verify forked PR CI restores cache and builds
- [ ] Verify same-repo PR CI uses JFrog OIDC unchanged

NO_CHANGELOG=true

This pull request was AI-assisted by Isaac.

---------

Signed-off-by: Gopal Lal <gopal.lal@databricks.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: gopalldb

.github/actions/setup-maven/action.yml

@@ -18,8 +18,8 @@ runs:
       uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
       with:
         path: ~/.m2/repository
-        key: ${{ runner.os }}-maven-deps-${{ hashFiles('**/pom.xml') }}
-        restore-keys: ${{ runner.os }}-maven-deps-
+        key: maven-deps-${{ hashFiles('**/pom.xml') }}
+        restore-keys: maven-deps-
 
     - name: Configure Maven without credentials (fork)
       if: inputs.is-fork == 'true'
@@ -106,5 +106,5 @@ runs:
       uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
       with:
         path: ~/.m2
-        key: ${{ runner.os }}-maven-deps-${{ hashFiles('**/pom.xml') }}
-        restore-keys: ${{ runner.os }}-maven-deps-
+        key: maven-deps-${{ hashFiles('**/pom.xml') }}
+        restore-keys: maven-deps-

.github/workflows/coverageReport.yml

@@ -47,7 +47,6 @@ jobs:
     - name: Run tests with coverage
       run: mvn -pl jdbc-core clean test -Dgroups='!Jvm17PlusAndArrowToNioReflectionDisabled' jacoco:report -Ddependency-check.skip=true
 
-
     - name: Check for coverage override
       id: override
       env:

.github/workflows/warmMavenCache.yml

@@ -29,12 +29,13 @@ permissions:
 
 jobs:
   warm-cache:
-    strategy:
-      matrix:
-        github-runner: [linux-ubuntu-latest, windows-server-latest]
+    # Run on Linux only. Maven repository contents (JARs/POMs) are platform-independent.
+    # Windows forked PRs restore this same cache via the restore-keys prefix match.
+    # Note: Windows runners in databricks-protected-runner-group lack bash, which
+    # is required for the OIDC token exchange scripts.
     runs-on:
       group: databricks-protected-runner-group
-      labels: ${{ matrix.github-runner }}
+      labels: linux-ubuntu-latest
 
     steps:
       - name: Set up JDK
@@ -144,4 +145,4 @@ jobs:
         uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
         with:
           path: ~/.m2/repository
-          key: ${{ runner.os }}-maven-deps-${{ hashFiles('**/pom.xml') }}
+          key: maven-deps-${{ hashFiles('**/pom.xml') }}