Renames: Consistent between imminent-event signals

[comods]

Imminent signals have been added with inconsistent naming.

My reasoning for consistency (weighed against each other): Reduced confusion (what timing? differentiated verb), consistent implied details (started what? cognitive load), cleaner reusable code (can: n in variant group: n.enabled = true), ease of knowing more features (A == B, A or B needed?), reduced double negatives, and reduced typing.

This Proposal is for the Imminent category to be consistent within itself, for the above reasons.

[comods]

Rename AA:

AA is for *_starts_next.

sort_children_starts_next (from pre_sort_children)
popup_starts_next (from pre_popup_pressed and about_to_popup)
draw_starts_next or draw_started (from frame_pre_draw)

[comods]

Rename CC:

CC is for *_is_next.

sort_children_is_next (from pre_sort_children)
popup_is_next (from pre_popup_pressed and about_to_popup)
draw_is_next or draw_started (from frame_pre_draw)

[comods]

Rename DD:

DD is for about_to_*.

about_to_sort_children (from pre_sort_children)
about_to_popup (from pre_popup_pressed and about_to_popup)
about_to_draw or draw_started (from frame_pre_draw)

[comods]

Rename BB:

BB is for pre_*.

pre_sort_children (from pre_sort_children)
pre_popup (from pre_popup_pressed and about_to_popup)
pre_draw or draw_started (from frame_pre_draw)

[comods]

This causes the least amount of renaming.