Feature Request: add support for multiple Gitlab instances

[agitatedlight]

Very similar to a feature request for the Sentry Plugin in the main Backstage repo (backstage/backstage#13333) could you please add the ability for the Gitlab plugin to be able to specify a specific instance to connect and fetch information - this will cover the scenario where there are multiple self-hosted Gitlab instances deployed within an organization.

[satrox28]

@agitatedlight Thanks for using the plugin, sure we will work on the feature request.