[FE] Update vsa chart endpoints"

What does this MR do?

Now that we always have a default value stream available, we should fetch all stage data from value_stream/:value_stream_id routes

• Updates the remaining chart and stage routes to include the current selected value stream.
• Removes the older groupStagesAndEvents route

Testing

1. Enable value_stream_analytics_create_multiple_value_streams
2. Create a new group
3. Browse to group VSA, for your new group /groups/<new-group-id>/-/analytics/value_stream_analytics
4. The create a value stream button should appear
5. Create a value stream, then the dropdown should appear allowing you to select a value stream or create another
6. Selecting a new value stream should refetch the stage table data and the chart data

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

Closes #221204 (closed) and #226996 (closed)