Determine property instance name API for all Properties

[CAD97]

We already have abbr_name, long_name, and human_name fn returning &'static str on EnumeratedCharProperty and BinaryCharProperty.

We should decide on if and how we want to expand these fn to NumericCharProperty and CustomCharProperty.

Because these have procedural name derivation from data, they will not be able to return &'static str, and will likely need to follow a fmt pattern or return String. Along with #144, we don't want to move further away from #![no_std] support in the UCD, so we probably want to favor the fmt API surface, though that is up for debate.

[CAD97]

See #168 and #169 for earlier context.