Feature request description

Requested by: https://github.com/sourcegraph/accounts/issues/570

Extend the functionality of the repo:has.topic() filter to support GitLab repository topics.
https://docs.sourcegraph.com/code_search/reference/language#repo-has-topic

Is your feature request related to a problem? If so, please describe.

Being able to filter repositories based on topics is crucial for repository management and search workflows.

Describe alternatives you've considered.

Using repo metadata.

/cc @sourcegraph/search-product