Use enif_term_type instead of enif_is_xyz when encoding

[lpgauth]

Form the OTP-22 changelog:

• Added the NIF function enif_term_type, which helps avoid long sequences of enif_is_xyz by returning the type of the given term. This is especially helpful for NIFs that serialize terms, such as JSON encoders, where it can improve both performance and readability.

[davisp]

Maybe in 5-6 years when 22 is old.

[davisp]

Oops. That was maybe more terse than I meant. For color, 23 has finally forced my hand to drop support for R14. Jiffy is small enough that I work on keeping it compatible with as many VM versions as possible.

That new API would be quite useful to add, but the complexity tradeoff if-def'ing around that wouldn't be worth it since we'd still have to maintain the if/else chain for type detection.