Remove legacy VSA stage table components

What does this MR do?

This MR is a follow up to #246493 (closed) and removes some code that is no longer needed.

Now that we have removed !60449 (merged), we can remove the old stage table components that are no longer in use.

This MR removes documentation for the old stage table flow.

Deleted components

• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_build_item.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_card_list_item.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_event_item.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_event_list.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_nav_item.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_table_header.vue
• ee/app/assets/javascripts/analytics/cycle_analytics/components/stage_table_nav.vue

Screenshots (strongly suggested)

No visual changes

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?) - no visual changes
• I have added/updated documentation, or it's not needed. (Is documentation required?) - Removed the old documentation
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• 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

Related to #323984 (closed)