[Misc] Add the step of downloading Jtreg in Actions

Summary: CICD

Testing: CI pipline

Reviewers: lei.yul, sendaoYan

Issue: dragonwell-project#858

.github/actions/get-jtreg/action.yml

@@ -39,6 +39,15 @@ runs:
       with:
         var: JTREG_VERSION
 
+    - name: 'Cache for JTReg'
+      run: |
+        mkdir -p jtreg/installed
+        jtreg_ver=`echo "${{ steps.version.outputs.value }}" | sed 's/+/./g'`
+        curl -L -o jtreg.tar.gz https://compiler-tools.oss-cn-hangzhou.aliyuncs.com/jtreg/jtreg-${jtreg_ver}.tar.gz
+        tar xf jtreg.tar.gz -C jtreg/installed --strip-components=1
+        rm -rf jtreg.tar.gz
+      shell: bash
+
     - name: 'Check cache for JTReg'
       id: get-cached-jtreg
       uses: actions/cache@v4