bug: no sanity check on storage layout files

[tserg]

Version Information

• vyper Version (output of vyper --version): 9e3b9a2
• OS: linux
• Python Version (output of python --version): 3.10.4

What's your issue about?

When compiling a contract with the flag storage_layout_file, some basic sanity checks could be performed on the given JSON file as currently:

• The JSON can have duplicated entries. In this case, the last one will be the one used by the compiler.
• The JSON can have entries not matching any storage slot of the contract
• The entries of the JSON do not necessarily have to match with the type of the corresponding variables in the contract.

For example, a contract only defining the storage variable a: uint256 can be compiled given the following storage layout:

{
    "a": {"type": "uint16", "slot": 10},
    "a": {"type": "uint8", "slot": 1},
    "b": {"type": "uint256", "slot": 1}
}

h/t @trocher

How can it be fixed?

Fill this in if you know how to fix it.

[cyberthirst]

roundtrip requirement was added in #3789