Add integration tests with the CLI

This commit adds integration tests that run commands using the CLI. This
change introduces a number of enhancements in order to get there.

1. Augments the index-template.ts file so that it downloads an
appropriate cli version if requested.
2. Adds the ensureCli.ts that performs the download if a a suitable
version is not already installed. See the comments in the file for how
this is done.
3. Changes how run-integration-tests is done so that the directories
run are specified through a cli argument.
4. Updates the main.yml workflow so that it also runs the
cli-integration tests.
5. Takes advantage of the return value of the call to `activate` on the
extension. This allows the integration tests to have access to internal
variables of the extension like the context, cli, and query server.
6. And of course, adds a handful of simple tests that ensure we have a
cli installed of the correct version.

.vscode/launch.json

@@ -77,6 +77,22 @@
       "outFiles": [
         "${workspaceRoot}/extensions/ql-vscode/out/**/*.js",
       ],
+    },
+    {
+      "name": "Launch Integration Tests - With CLI",
+      "type": "extensionHost",
+      "request": "launch",
+      "runtimeExecutable": "${execPath}",
+      "args": [
+        "--extensionDevelopmentPath=${workspaceRoot}/extensions/ql-vscode",
+        "--extensionTestsPath=${workspaceRoot}/extensions/ql-vscode/out/vscode-tests/cli-integration/index",
+        "${workspaceRoot}/extensions/ql-vscode/test/data"
+      ],
+      "stopOnEntry": false,
+      "sourceMaps": true,
+      "outFiles": [
+        "${workspaceRoot}/extensions/ql-vscode/out/**/*.js",
+      ],
     }
   ]
 }