extension_ci: Allow some more time for tests job (#49900)

Gives the compilation in a repository with a few more grammars some more
time to run. Also adds the Rust cache which might be utilized here
during Rust compilation.

Release Notes:

- N/A

.github/workflows/extension_tests.yml

@@ -99,6 +99,11 @@ jobs:
       run: |
         wget --quiet "https://zed-extension-cli.nyc3.digitaloceanspaces.com/$ZED_EXTENSION_CLI_SHA/x86_64-unknown-linux-gnu/zed-extension"
         chmod +x zed-extension
+    - name: steps::cache_rust_dependencies_namespace
+      uses: namespacelabs/nscloud-cache-action@v1
+      with:
+        cache: rust
+        path: ~/.rustup
     - name: extension_tests::check
       run: |
         mkdir -p /tmp/ext-scratch
@@ -132,7 +137,7 @@ jobs:
             echo "Version changes happen in separate PRs and will be performed by the zed-zippy bot"
             exit 42
         fi
-    timeout-minutes: 4
+    timeout-minutes: 6
   tests_pass:
     needs:
     - orchestrate