Rename files in pipeline mini graph, stub out new files

What does this MR do and why?

Part 2 of 3 for #384853 (closed)

This is essentially just a big file rename MR. The code is behind a feature flag and is in a transitional state. I have stubbed out a couple of components to allow for some GraphQL logic.

Everything should function exactly the same except for the pipeline mini graphs in the commit page and the pipeline editor page. For now, these components should simply show a stage ID in place of the pipeline stages.

THIS MR

• Rename pipeline_stage.vue > legacy_pipeline_stage.vue
• Add in a new pipeline_stage.vue for GraphQL data
• Rename pipeline_mini_graph/job_item.vue > pipeline_mini_graph/legacy_job_item.vue
• Add in a new job_item.vue for GraphQL data

Renamed files

• anything prepended with legacy...

New stubbed files

• pipeline_stages.vue
• pipeline_stage.vue
• job_item.vue
• specs for above

NEXT MR

• Add in code/logic for fetching stage by ID
• Remove the formattedStages portion of pipeline_mini_graph.vue because this will no longer be needed.
• Update specs

Screenshots or screen recordings

Commit Page Normal	Commit Page Current	Pipeline Editor Normal	Pipeline Editor Current

**All other pipeline mini graphs are legacy and should look the same.

How to set up and validate locally

1. Feature flag - Feature.enable(:ci_graphql_pipeline_mini_graph)
2. Navigate to any commit. You should see stage IDs instead of stages
3. Navigate to the Pipeline editor. You should see stage IDs
4. The pipeline mini graphs in the pipeline tables as well as MR page pipeline mini graph should be the same

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.