Value Stream Analytics: Migrate project selector into GlFilteredSearch

In #217943 (closed) we introduced filters for Value Stream Analytics.

This solution still uses both a project dropdown and the filter bar. We should migrate the project dropdown by enabling users to select a project from the filter bar.

This requires the following changes:

• Remove the project dropdown
• Add a new project token to the GlFilteredSearch implementation.
• Make sure that milestone and label filters won't be available until a project has been selected (since they depend on the selected project)
• When a user changes the project, any applied milestone or label filters need to be removed since they might not be available on the selected project anymore.