Resolve "Productivity Analytics: MR table showing zeros in "Time to merge" column"

What does this MR do?

This MR adds the metricTypes to the root state so they can be shared across all store modules. By this, metricTypes can be used by all charts and the MR table (via getMetricTypes). With this change tableSortFields gets obsolete since the MR table uses metricTypes as well.

In addition, it this MR ensures that the days_to_merge metric is displayed in the Time to merge column in the MR table on the Productivity Analytics pages and that the dropdown options in the last column lists the following options:

• 'Time from first commit until first comment' (time_to_first_comment)
• 'Time from first comment to last commit' (time_to_last_commit)
• 'Time from last commit to merge' (time_to_merge)

This is behind the productivity_analytics feature flag.

Screenshots

Before	After

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

Closes #32068 (closed)