Add fine grained capabilities for managing app passwords

[TimothyBlynJacobs]

Currently, app passwords check the edit_user meta capability. Ideally, we'd introduce a set of more fine grained capabilities for managing app passwords. This might be as simple as an manage_app_passwords meta cap that follows the same mapping as edit_user, or we could be more fine-grained and have list_app_passwords, create_app_passwords, etc...

[carike]

Watching because I'm interested to see if there are any good alternatives to introducing new primitive caps.
If it is time to introduce new primitive caps (perhaps in a "staggered" way so that a DB upgrade is not needed), the privacy component and media are also sorely in need of new caps, so co-ordination on this would be great.

Trac ticket: https://core.trac.wordpress.org/ticket/51703

[TimothyBlynJacobs]

@johnbillion If you have a chance, could you take a look at the patch for this?

Thanks for the review! Great point, I've deprecated it in 9972c38.

[TimothyBlynJacobs]

In 50114:

App Passwords: Introduce fine grained capabilities.

Previously, all permission checks for using app passwords were implemented using edit_user. This commit introduces a series of more fine grained meta capabilities that should be used instead: create_app_password, list_app_passwords, read_app_password, edit_app_password, delete_app_password and delete_app_passwords. These capabilities all map to edit_user by default, but may now be customized by developers.

Props johnbillion, TimothyBlynJacobs.
Fixes #51703.

Merged in ​https://github.com/WordPress/wordpress-develop/commit/c8f974f2f5c5f3de670703d49547f0976dc343ab.