"pre_add_option" hook missing

[kkmuffme]

There's a "pre_add_site_option_" (and a "pre_update_") apply_filters, but no "pre_add_option_" hook

Since there recently was some discussion about adding one for "delete" too https://core.trac.wordpress.org/ticket/44042 I guess it would make sense to also add the hook for "add".

This would also ensure the commonly used "workaround" (where "pre_update_" is filtered) of using delete_option => add_option can be prevented.

Trac ticket: https://core.trac.wordpress.org/ticket/63685