Media: Do not update attachment display user settings when a single attachment is inserted.

This is consistent with 3.4 behavior.

see #22841.
Media: Restore 3.4 behavior by consulting the old-school DB options for default align, size, and link properties.

This restores linking to media files as the default, over attachment pages. This 'default' cannot currently be changed by a user setting (per 3.4 behavior), due to the default database schema.

see #22841, for trunk.
Media: Properly reset the "add to gallery" library to ensure it accurately reflects the current gallery. see #22815.
Media: Pass thumbnail and medium sizes to image_constrain_size_for_editor() to force constraints based on the current DB options for those sizes. History: see #22598, #22738.

props jond3r.
see #23102.
for trunk.