Merge Requests: sort alphabetically

What does this MR do and why?

Adds the ability to sort merge request lists by title, in the UI and the GraphQL/REST apis.

Related MRs:

• Resolve "Issues: sort alphabetically" (!67234 - merged)
• Epics: Sort Alphabetically (#331625 - closed)

Describe in detail what your merge request does and why.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally

1. Go to a project's merge request list, and sort by Title. Should be able to sort asc and desc.

2. Go to your global merge request list (icon in upper right), and sort by Title. Should be able to sort asc and desc.

3. You can use the following query in graphql-explorer, http://localhost:3000/-/graphql-explorer

   query {
     project(fullPath: "flightjs/Flight") {
       mergeRequests(sort: TITLE_DESC) {
         nodes {
           title
         }
       }
     }
   }

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.

Related to #337136 (closed)