Delete profile field meta when field is deleted

[boonebgorges]

From #4275:

I think it would be better to delete the xprofile meta created for fields if the field is deleted by the admin so in the same file in the function xprofile_admin_delete_field, i suggest to add this line before the do_action( 'xprofile_fields_deleted_field', $field );

bp_xprofile_delete_meta( $field_id, 'field' );

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We do *not* appear to delete item meta after deleting items throughout BP (groups, activity). Perhaps we should, but it needs some testing and discussion.

[slaFFik]

We can also add own add_action( 'xprofile_fields_deleted_field', 'bp_xprofile_delete_meta') etc for other components.
Thus we will also allow developers to unhook this (now sure why, though).
We already use this hook to clear cache.

[DJPaul]

We're closing this ticket because it has not received any contribution or comments for at least two years. We have decided that it is better to close tickets that are good ideas, which have not gotten (or are unlikely to get) contributions, rather than keep things open indefinitely. This will help us share a more realistic roadmap for BuddyPress with you.

Everyone very much appreciates the time and effort that you spent sharing your idea with us. On behalf of the entire BuddyPress team, thank you.

If you feel strongly that this enhancement should still be added to BuddyPress, and you are able to contribute effort towards it, we encourage you to re-open the ticket, or start a discussion about it in our Slack channel. Please consider that time has proven that good ideas without contributions do not get built.

For more information, see ​https://bpdevel.wordpress.com/2018/01/21/our-awaiting-contributions-milestone-contains/
or find us on Slack, in the #buddypress channel: ​https://make.wordpress.org/chat/