Fixes: Auto-remediation on the pipeline security dashboard

What does this MR do?

This MR moves the pipeline dashboard into its own wrapper component so we can set the sourceBranch properly.

It also adds the appropriate actions and mutations to do so.

This fixes a bug where creating a remediation MR from a pipeline would fail as it had no context of which branch to apply the MR to and would default to the default branch.

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

Touches #119040 (closed)