Add pre-filter to bp_avatar_get_avatars_history() for custom storage backends

[GaryJ]

On hosting platforms like WordPress VIP, the filesystem uses a custom stream wrapper that doesn't support FilesystemIterator directory listing. This causes a fatal error when BuddyPress tries to enumerate avatar history.

The ​buddypress-vip-go plugin handles avatar uploads by storing data in user meta. However, there's no way to provide avatar history from meta because bp_avatar_get_avatars_history() directly accesses the filesystem.

Currently, the only workaround is add_filter( 'bp_disable_avatar_history', '__return_true' ) which removes the Recycle feature entirely.

Proposed Change

Add a pre-filter to bp_avatar_get_avatars_history():

$pre_history = apply_filters( 'bp_pre_avatar_get_avatars_history', null, $item_id, $object, $type );
if ( null !== $pre_history ) {
    return $pre_history;
}

This follows the same pattern as bp_core_pre_avatar_handle_upload and bp_attachments_pre_get_attachment.

Trac ticket: ​https://buddypress.trac.wordpress.org/ticket/9311

[espellcaste]

In 14151:

Add pre-filter hook for avatar history.

Add bp_pre_avatar_get_avatars_history filter to allow short-circuiting avatar history retrieval.
Fix typo @parma to @param in bp_core_avatar_handle_upload docblock.

Props GaryJ.

See #9311 (14.0)

[espellcaste]

In 14152:

Add pre-filter hook for avatar history.

Add bp_pre_avatar_get_avatars_history filter to allow short-circuiting avatar history retrieval.
Fix typo @parma to @param in bp_core_avatar_handle_upload docblock.

Props GaryJ.

Closes ​https://github.com/buddypress/buddypress/pull/426/
Fixes #9311 (trunk)