Rename WIP merge requests to Draft

Problem to solve

WIP limits are being added to issue boards #11403 (closed) which creates a naming collision with WIP (Work In Progress) merge requests.

Furthermore, WIP merge requests are frequently used to mean "this MR is a draft, please don't merge" even though they are complete and ready for review.

Further details

The acronym "WIP" is not commonplace in software community worldwide and even less so for non-english speakers. "Draft" is a more inclusive and self-explanatory term.

Proposal

1. Rename the feature Draft
2. Reword title subtext in MR edit mode from:
   “Start the title with WIP: to prevent a Work In Progress merge request from being merged before it's ready.”
   to
   “Start the title with Draft: or WIP: to prevent a merge request that is a work in progress from being merged before it's ready.” “Remove the [Draft|WIP] prefix from the title to allow this merge request to be merged when it's ready.”
3. Add support for Draft:, [Draft], (Draft), or Draft - case insensitive prefixes in:
   1. The merge request title.
   2. Commit messages targeting the merge request’s source branch.
4. Reword the MR widget when in draft state:
   

While WIP deprecation is active, we should support both WIP and Draft prefixes for MRs and commit messages

Future work

1. Rename the WIP filter in the merge request list. We would need to change it in a way that doesn't break old URLs that still use it: #227414 (closed)
2. Rename or add a new /draft alias to the /wip quick action: #227415 (closed)

Links / references