Add test for exportResultsToGist method

While we're here we're also adding a test for the `exportResultsToGist`
method, as there were no tests for the `export-results.ts` file.

We initially attempted to add the test to the pure-tests folder, but the
`export-results.ts` file imports some components from `vscode`, which
meant we needed to set up the test in an environment where VSCode
dependencies are available.

We chose to add the test to `vscode-tests/no-workspace` for convenience,
as there are already other unit tests there.

We've also had to import our own query and analysis result to be able
to work with data closer to reality for exported results.

Since we've introduced functionality to build a gist title, let's check
that the `exportResultsToGist` method will forward the correct title to
the GitHub Actions API.

Co-authored-by: Shati Patel <shati-patel@github.com>

Author: elenatanasoiu

extensions/ql-vscode/src/remote-queries/export-results.ts

@@ -74,7 +74,7 @@ async function determineExportFormat(
 /**
  * Converts the results of a remote query to markdown and uploads the files as a secret gist.
  */
-async function exportResultsToGist(
+export async function exportResultsToGist(
   ctx: ExtensionContext,
   query: RemoteQuery,
   analysesResults: AnalysisResults[]