[AUTH-PLUGIN] caching_sha2_password is still not supported

[linyu003]

[sidorares]

I'll close this one as a duplicate. The plugin is supported, but not in a most efficient way. If the server wants to use caching_sha2_password after clients initial mysql_native_password the server sends AUTH_PLUGIN_SWITCH response and the client then switches to caching_sha2_password

#2143 tracks the 'use correct plugin in the initial client hello packet'