Global Search - Dropdown Filters

What does this MR do?

Closes #262056 (closed)

This change introduces a top level Search Vuex Store that will be shared between the upcoming Search components.

This change also cleans up the implementation of the Dropdown filter to be Data-Driven. The files were a little spread out and it was hard to see from the file explorer the connection. This change brings them all into the same folder and creates data folders for the data-driven aspects of the components

Screenshots

header	Before	After (identical)
Search UI

GIF

Existing functionality works

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team