Add cycle time to Value Stream Analytics summary

What does this MR do?

Original issue #21863 (closed)

This MR adds cycle time to the summary for a group under Value Stream Analytics, where

Cycle time is the time between when the production of a product is started and when it is completed. This is typically taken as the time between when an engineer begins work on an issue/feature to the time that it is merged or deployed.

This MR is part of 3-part BE work (Re-factoring of group summary and adding lead time to VSA summary)

Eventually, this summary will be displayed as part of pending FE work here, but this BE MR can be merged independently.

This MR is part of a series that needs to be merged in this order:

1. !28201 (merged)
2. !29572 (merged) <-- this MR
3. !29791 (merged)

Screenshots

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