CLDR-11585 cache maven dependencies (#738)

- cache maven dependencies for build speedup and reliability
- do not specify the maven central URL but let it default
- update some action versions
- do not run tests twice!

- also, add a comment explaining a line in the ansible-lint.yml
(from CLDR-13771 workaround ansible-lint failing (#729) )

(cherry picked from commit 880b495)

.github/workflows/ansible-lint.yml

@@ -10,6 +10,7 @@ jobs:
       with:
         lfs: false # not needed for this job, as we don’t currently do a Java build
     - name: Lint Ansible Playbook
+      # the hash here is a specific version of that repo, since there is not a later commit.
       uses: ansible/ansible-lint-action@6c8c14186662e43effbe39a678950896a46799ad
       with:
         targets: |

.github/workflows/maven.yml

@@ -11,17 +11,23 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
-
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.3
         with:
           lfs: true
       - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
+        uses: actions/setup-java@v1.4.2
         with:
           java-version: 1.8
+      - name: Cache local Maven repository
+        uses: actions/cache@v2.1.1
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('tools/**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
       - name: Build with Maven
-        run: mvn -s .github/workflows/mvn-settings.xml -B package --file tools/pom.xml
+        run: mvn -s .github/workflows/mvn-settings.xml -B package --file tools/pom.xml -DskipTests=true
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Test with maven

.github/workflows/mvn-settings.xml

@@ -18,12 +18,7 @@ TODO: Remove this when ICU-21251 is completed.
     <profile>
       <id>github</id>
       <repositories>
-        <repository>
-          <id>central</id>
-          <url>https://repo1.maven.org/maven2</url>
-          <releases><enabled>true</enabled></releases>
-          <snapshots><enabled>true</enabled></snapshots>
-        </repository>
+        <!-- the 'central' repository is already defined by default. -->
         <repository>
           <id>github</id>
           <name>GitHub unicode-org/cldr Apache Maven Packages</name>