Plugin deletion results must be stored in an option instead of a transient to avoid the transient being removed on shutdown

[kkmuffme]

​https://github.com/WordPress/wordpress-develop/blob/trunk/src/wp-admin/plugins.php#L431

When using an external object cache, if any plugin hooks wp_cache_flush on shutdown hook/register shutdown function, this transient will be removed and the plugin delete result is never shown to the user.

The result should be stored in an option instead of a transient to fix this problem.

You could argue that you shouldnt call cache flush on shutdown, however this is often the only way to fix compatibility issues where plugins do not remove their data from cache on uninstall and you are left with a broken site after uninstalling.

Store delete result in non-autoloaded option instead of cache/transient to ensure it cannot be accidentally removed by other plugins that flush the cache.

[swissspidy]

In 57586:

Plugins: Store plugin deletion results in temporary option.

Storing the data in a non-autoloaded rather than a transient ensures it cannot be accidentally removed due to a cache flush.

Props: kkmuffme, mukesh27.
Fixes #59433.