[Workflows] Enable commit access requests via GitHub issues (#100458)

This updates the auto-labeler to match a specific issue title that is
going to be used for requesting commit access and then add the
infrastructure:commit-access-request label.

This will notify the admin team who will be able to handle the request.

See
https://discourse.llvm.org/t/rfc-change-the-process-for-requesting-commit-access/80184

---------

Co-authored-by: Vlad Serebrennikov <[email protected]>

Author: tstellar

.github/new-issues-labeler.yml

@@ -27,3 +27,6 @@
 
 'bolt':
   - '/\bbolt(?!\-)\b/i'
+
+'infra:commit-access-request':
+  - '/Request Commit Access/'

llvm/docs/DeveloperPolicy.rst

@@ -533,13 +533,13 @@ Obtaining Commit Access
 -----------------------
 
 We grant commit access to contributors that can provide a valid justification.
-If you would like commit access, please send an email to
-`Chris <mailto:[email protected]>`_ with your GitHub username.  This is true
-for former contributors with SVN access as well as new contributors. If
-approved, a GitHub invitation will be sent to your GitHub account. In case you
-don't get notification from GitHub, go to
+If you would like commit access, please use this `link <https://github.com/llvm/llvm-project/issues/new?title=Request%20Commit%20Access%20For%20%3Cuser%3E&body=%23%23%23%20Why%20Are%20you%20requesting%20commit%20access%20?>`_ to file
+an issue and request commit access. Replace the <user> string in the title
+with your github username, and explain why you are requesting commit access in
+the issue description. If approved, a GitHub invitation will be sent to your
+GitHub account. In case you don't get notification from GitHub, go to
 `Invitation Link <https://github.com/orgs/llvm/invitation>`_ directly. Once
-accept the invitation, you'll get commit access.
+you accept the invitation, you'll get commit access.
 
 Prior to obtaining commit access, it is common practice to request that
 someone with commit access commits on your behalf. When doing so, please