Rename BuildpackKind::LibCnbRs to something clearer

[edmorley]

since we're renaming, i wonder if LibCnbRs should be renamed to something like CompilableComponent or LibCnbComponent. not necessary but the current name looks like an unpronounceable string of consonants 😅

Originally posted by @colincasey in #682 (comment)

This is in reference to:

libcnb.rs/libcnb-package/src/buildpack_kind.rs

Lines 21 to 25 in c194868

	pub enum BuildpackKind {
	LibCnbRs,
	Meta,
	Other,
	}