private method to get an object key, then consume the colon which should follow

Parse a JSON enum from a byte slice, returning a borrowed version of the enum - e.g. strings can be references into the original byte slice.

Parse a JSON enum from a byte slice, returning an owned version of the enum.

Note - caching strings should make no difference here

# Safety `accii_only` must only be set to true if the string is ascii only

Basic sanity check that running a parse in multiple threads is fine.