Fix broken extension packaging

When we tried to release the extension yesterday, packaging the extension failed: https://gitlab.com/gitlab-org/gitlab-vscode-extension/-/jobs/1091162479

The error was:

$ npx vsce package
 ERROR  @types/vscode ^1.54.0 greater than engines.vscode ^1.51.0. Consider upgrade engines.vscode or use an older @types/vscode version

The version mismatch has been introduced by chore(npm): run npm upgrade to update all dependencies.

This MR is fixing both the error and the process (two separate commits):

1. We downgrade the @types/vscode to match the specified package.json.engines.vscodde
2. We run the package task on every pipeline to prevent merging MRs that break packaging