Productivity Analytics: Add MR table to app

What does this MR do?

This is one of many MRs for the new Productivity Analytics page.

This MR renders the MR Table Component introduced in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14757 on the Productivity Analytics app and wires it to the API.

Additional changes introduced:

• When no groupNamespace is set, an empty state SVG is rendered.
• Adds pagination to the table
• Adds the table store module including relevant getters, actions and mutations/mutation_types.
• Adds specs for the table store module

Note: Without the API changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14772, this cannot be tested locally. This is behind the productivity_analytics feature flag and which will be enabled once https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14772 is merged.

Screenshots

Empty screen	With data

Screencast

mr_table_screencast

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

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