Altered access & usage of the /search/users/select endpoint with the
following changes:
- Removed searching of email address to prevent email detail discovery
via hunting via search queries.
- Required the user to be logged in and have permission to manage users
or manage permissions on items in some way.
- Removed the user migration option on user delete unless they have
permission to manage users.
For #3108
Reported in https://huntr.dev/bounties/135f2d7d-ab0b-4351-99b9-889efac46fca/
Reported by @haxatron
- Primarily moved and re-organised view files.
- Included readme within views to document the convention.
- Fixed some issues with page field select list in previous commit.
- Tweaked some route names while going through.
- Split some views out further.
Closes#2805
