ci: speed up test with matrix (#1830)

* add an action to install pnpm packages
* add an action to prepare build environment
* rewrite test workflow, using composite actions and matrix

.github/actions/prepare-pnpm/action.yml

@@ -0,0 +1,42 @@
+name: 'Setup pnpm'
+author: Luna
+description: 'Setup Node.js, pnpm, and install dependencies'
+
+inputs:
+  build_filter:
+    description: 'The filter argument for pnpm build (e.g. ./easytier-web/*)'
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Setup Node.js
+      uses: actions/setup-node@v4
+      with:
+        node-version: 22
+
+    - name: Install pnpm
+      uses: pnpm/action-setup@v4
+      with:
+        version: 10
+        run_install: false
+
+    - name: Get pnpm store directory
+      shell: bash
+      run: |
+        echo "STORE_PATH=$(pnpm store path --silent)" >> $GITHUB_ENV
+
+    - name: Setup pnpm cache
+      uses: actions/cache@v4
+      with:
+        path: ${{ env.STORE_PATH }}
+        key: ${{ runner.os }}-pnpm-store-${{ hashFiles('**/pnpm-lock.yaml') }}
+        restore-keys: |
+          ${{ runner.os }}-pnpm-store-
+
+    - name: Install and build
+      shell: bash
+      run: |
+        pnpm -r install
+        echo "Building with filter: ${{ inputs.build_filter }}"
+        pnpm -r --filter "${{ inputs.build_filter }}" build