Recovery mode: infinite redirect

[azaozz]

Happens when trying to reactivate faulty plugin that has been deactivated (from the "Paused plugins" screen).

Steps to reproduce:

1. Introduce a fatal error in a plugin.
2. Access the site. It will fail to load and trigger Recovery Mode. Click the link in the email and log in.
3. Go to the "Paused plugins" screen and deactivate the plugin.
4. Go to "All plugins" and try to reactivate it.

[afragen]

Possibly related. Happens when trying to initially activate a plugin with a fatal.

1. Create a plugin with a fatal error.
2. Activate the plugin and Recovery Mode is not triggered.

Difference seems to be when the fatal is introduced, after the plugin has been activated or before.

[flixos90]

This will be fixed by https://core.trac.wordpress.org/ticket/46045#comment:13.

[flixos90]

In 45114:

Bootstrap/Load: Ensure WP_Fatal_Error_Handler does not conflict with existing mechanisms treating fatal errors.

Prior to this change, resuming or activating a plugin or theme that is still broken would result in a redirect loop if in recovery mode. If outside recovery mode, it would cause the error template to be displayed.

Furthermore this applies to breaking a plugin or theme when editing from the backend.

Props aandrewdixon, azaozz, dhanukanuwan, henrywright, ocean90, ohiosierra, PandelisZ, xkon.
Fixes #46045, #46751.