Simplify Byte Implementations

[blitz]

I'm trying to wrap my head around the different read/write functions in the Byte trait. It seems a bit needlessly intimidating and confusing. For reference, I'm refering to these functions: https://docs.rs/vm-memory/0.7.0/vm_memory/bytes/trait.Bytes.html#tymethod.read

1. write writes to the Byte object, but write_to actually reads from it. read_into could have been a better name.
2. Most read/write functions could have default implementations based on read/write but that seems to be prevented by the configurable error type.

Are these desirable changes?

[andreeaflorescu]

I am myself a bit confused about these things, @bonzini @alexandruag @jiangliu do you have a better idea how to answer here?