Move [AdviceGlottalStopArchDepth] from meta/aesthetics.ptl to letter/latin-ext/glottal-stop.ptl.

[jmcwilliams403]

This function is only ever used by Glottal Stop itself and Digit 2 (2).

Since Digit 3 (3) derives one of its shape variants based on Latin Ezh (Ʒ, ʒ), a letter that's also defined in letter/latin-ext/, I think it's fine if Digit 2 imports its arch depth function directly from letter/latin-ext/glottal-stop.ptl.

This is also consistent with certain mathematical characters importing arch depth values for Latin S (S, s) directly from letter/latin/s.ptl.

Also fix sign argument for arch depth of Glottal Stop with Curl (𝼎), which was backwards before. This defect is made more clear in the code when going through and labeling each instantiation of the function as either local ada or local adb for each character individually.