Use WarpBuild runners for CI workflows (#600)

Migrate CI, integration, docker, and release-docs workflows from
ubuntu-latest to warp-ubuntu-latest-x64-4x for faster builds and
improved caching. Release and CLA workflows are left on GitHub-hosted
runners.

Author: tillrohrmann

.github/workflows/docker.yaml

@@ -15,7 +15,7 @@ env:
 jobs:
   sdk-test-docker:
     if: github.repository_owner == 'restatedev'
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     name: "Create test-services Docker Image"
 
     steps:

.github/workflows/integration.yaml

@@ -61,7 +61,7 @@ on:
 jobs:
   sdk-test-suite:
     if: github.repository_owner == 'restatedev'
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     name: "Features integration test"
     permissions:
       contents: read

.github/workflows/release-docs.yml

@@ -21,7 +21,7 @@ concurrency:
 jobs:
   build-javadocs:
     name: Build Javadocs/KtDocs
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     timeout-minutes: 10
     steps:
       - uses: actions/checkout@v4
@@ -48,7 +48,7 @@ jobs:
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     needs: build-javadocs
     steps:
       - name: Deploy to GitHub Pages

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ on:
 jobs:
   build-and-test:
     name: Build and test (Java ${{ matrix.java }})
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     timeout-minutes: 10
     strategy:
       fail-fast: false
@@ -42,7 +42,7 @@ jobs:
 
   test-javadocs:
     name: Test Javadocs and dokka
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     timeout-minutes: 10
     steps:
       - uses: actions/checkout@v4
@@ -62,7 +62,7 @@ jobs:
 
   event_file:
     name: "Event File"
-    runs-on: ubuntu-latest
+    runs-on: warp-ubuntu-latest-x64-4x
     timeout-minutes: 10
     steps:
       - name: Upload