Standardize TW/HK 八 and 入 components with JP/KR forms

I propose making the TW/HK forms of 八 (TW only) and 入 (especially the length of the top horizontal stroke that is connected to the throw stroke on the right) follow that of the JP/KR designs. This will make the glyphs more consistent and ensures better readability.

This will involve adjusting some TW glyphs, and even restoring some v1 JP glyphs (or adding JP glyphs that was designed but never made it to v1) to replace the current TW glyph if needed.

Doing this will also free up some CIDs as well, probably in the hundreds.

Here are the examples of the discrepancy between the length of the horizontal strokes between JP/KR and TW/HK, in Sans and Serif.

For the 公 component, all the TW glyphs containing this should be manually adjusted to match the balance of JP/KR glyphs because the bottom 厶 part is not unifiable.

Again, I’m giving a commercial font as a reference for why I am proposing this change, even though by right we should not copy another typeface. Hiragino Sans CNS (TW) keeps the length of the 八 and 入 components similar to the JP locale (if set to JIS78 forms).

Also, quoting from [this issue on Serif](https://github.com/adobe-fonts/source-han-serif/issues/109):
> I am aware that the font is using two slightly different designs for JP/KR and TW/HK, like below:
>
> 
>
> The only difference is the length of the horizontal line of 入 (TW/HK is slightly shorter). This, to me, is actually a unifiable difference. Which is why I am not suggesting new glyphs be added.

I will list the glyphs affected in the coming weeks, along with a separate version for Serif. I did list glyphs for the 全 component [in the same issue page as above](https://github.com/adobe-fonts/source-han-serif/issues/109#issuecomment-1022060778), but I will create a more comprehensive list soon which will also include 八.

Start with the attached Sans and Serif comparison images and the linked Source Han Serif issue to understand the proposed 八, 入, 公, and 全 component differences. The issue says a comprehensive affected-glyph list will be provided; completion would require that list and the corresponding TW/HK glyph adjustments, but no files or tests are named.

Vom Indexierungsmodell aus dem Issue-Text verfasst.