Consider replacing all Linus Libertini Greek letters with STIX2 ones

[kiwi0fruit]

See https://github.com/kiwi0fruit/open-fonts/issues/5 for screenshots and https://github.com/libertinus-fonts/libertinus/issues/132 for discussion.

• Replace all Greek Unicode section all together in Linus Libertini and Linus Libertini Math with STIX2 one. Also replace Math Greek of different styles.
• Should be linear treansform for every R, I, B, BI styles and lowercase and uppercase.
• Replace double story g with single story one for italics (in default stylistic sets) https://github.com/libertinus-fonts/libertinus/issues/133
• As a bonus: monitore ы ь ъ like in https://github.com/libertinus-fonts/libertinus/issues/74

[kiwi0fruit]

I guess I won't have motivation to fix it as I can always use Source Serif Pro with STIX Two Text fallback and STIX Two Math.