Make four Gamma/H-derived characters respond to cv08/cv56.

[jmcwilliams403]

I feel like this is a better implementation for the serifs of these particular characters than my earlier PR's around them.
ref: #2095 #2080 #2269

• Lower Digamma and the right half of Cyrillic En-Ghe will respond to the top-right serifs Greek Gamma.
  • If Gamma is completely unserifed (or only bottom serifed), then En-Ghe will eject the top-right serif of its En part for balancing and disambiguation.
• Lower Heta will respond to top-left serif variants of H.
  • this also reduces glyph count overall due to the single auto-serifed variant that affected all H characters.

All Greek Capital Gamma variants:
Γ𝝘ϜϝГ㥴Ҥҥ
sans:

slab:

All H variants:
H𝖧ⱧⱵⱶꟵꟶͰͱǶꞪЊҤ
sans:

slab:

All Cyrillic Lower En variants:
нңњҥԋ
sans:

slab: