Provide an option to filter out WIP Merge requests in the Merge Requests page

Problem to solve

Currently, there is no way to filter out the Work in Progress Merge requests. It will be a lot easier for the reviewer to filter out the WIP Merge requests and see only relevant MRs.

Proposal

Currently, there are options to filter the MRs various ways.
Along with that provide an extra option to exclude the WIP MRs