[Wi-Fi] Do not delete certs when forgetting network

Deleting EAP Wi-Fi configuration deletes shared credentials used by other
configs. To resolve this issue the following changes were implemented:
1. When manually adding Wi-Fi certs from storage, Wi-Fi will not attempt
to delete them when network is removed.
2. When apps use WifiEnterpriseConfig#setClientKeyEntry to add certs,
they will be deleted if the network is removed.
3. Allow the user to delete Wi-Fi certs the same way that allows the
user to add them. Make the "Remove" option available, and implement key
store removal in settings.

Bug: 30248175
Test: atest WifiEnterpriseConfigTest
Test: Load certs, remove certs from credentials menu
Test: Load cert, create 2 EAP networks that use it, forget one network
Change-Id: I2015207d51188821da3397e1947e5eb6aefbf6e1