Support MR search scope for pipelines

Problem to solve

Users of Pipelines for Merged Results and Merge Trains want to be able to locate the pipeline that is related to a particular change connected to a merge train or merged result. This is not possible today.

Users have stated it is difficult to find what pipelines are merge train pipelines when a lot of pipelines are currently running.

Proposal

Support users being able to search for pipelines by MR scope

1. Navigate to Build > Pipelines
2. Have the ability to filter pipelines by MR scope such as "merge train" or "merged result"