Release 3.0.0

[ia0]

Required tasks:

• [x] Use static dispatch instead of dynamic dispatch
• [x] Use static instead of const for pre-defined encodings
• [x] Make Encoding implementation private
• [x] Add _uninit() version to support MaybeUninit outputs
• [x] Move development work in lib/v3
• [ ] Make encode_len() return a Result such that {en,de}code_len() return an error (could be a new ErrorKind::Overflow) in case the following arithmetic would overflow by computing the bound and documenting it (see #145)
• [ ] Introduce explicit traits to avoid users seeing True and False (also useful to avoid parameter ordering issues)
• [ ] Restrict symbols to printable/graphical ASCII?
• [ ] Do we really need wrapping separator of up to 255 bytes? Seems like 15 would be enough.
• [ ] Add a third option for padding: NoPad, PadConcat, PadFinal (new). [context]
• [ ] Do not panic for recoverable errors, return an error instead (see #126) actually we should be no-panic on no-alloc
• [ ] It should be possible to define custom encodings with const fn
• [ ] Figure out MSRV (in particular if 1.84 would solve the problem definitely)
• [ ] Update documentation once satisfied with the design
• [ ] Update OSS-Fuzz to also fuzz lib/v3

Optional tasks:

• [ ] Consider whether wrapping should be limited to multiple of the decoding block (use case)
• [ ] Identify and fix performance regression with "wrap" functions
• [ ] Add SIMD support (see #95)
• [ ] Consider whether a "short input" engine for base58, nix-base32, etc would be worth it (see #110)

After release:

• [ ] Update OSS-Fuzz if needed