Add more utilities to handle common layer creation scenarios

[samj1912]

It would be useful to have some handy utilities to compare layer metadata and "reset" layers when they don't match.

For eg. something like this is implemented in libpak via a new layer contributor. Maybe we should consider adding something similar to libcnb as it feels like a fairly common and generic use case.

FWIW the python version of libcnb which heavily borrows ideas and Apis from this go version has some similar utilities for layer metadata comparison, loading the metadata and resetting the layer https://samj1912.github.io/python-libcnb/api/#libcnb._layers.Layer for an idea of what this could look like in libcnb

[loewenstein]

@samj1912 is this in the 2.0 milestone because it cannot be done in 1.x or because it is a requirement to release 2.0?

cc @dmikusa