Add projectSelector store module to security dashboards

What does this MR do?

This MR introduces a new store module to the security dashboard.

It is largely based off an existing store module (ee/app/assets/javascripts/vue_shared/dashboards/store) but includes some changes that aim to make it more generic and usable for the instance-level security dashboard:

• Removal of etags polling related actions and mutations
• More detailed state around the request lifecycle of adding and removing projects
• Jest tests
• Generic error messages

In its current state the module's purpose will be the driving of the new Instance Security Dashboard's project selector. The addition of which will happen in a separate MR.

Note: This MR does not add any changes that actually wire up the module with any stores.

Screenshots

Not applicable: This MR does not introduce any UI changes.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Performance 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