Changed Instruction Indices Prevent Importing of Paths

[dhulliger]

Working on a bndb can lead to altered MLIL instruction indices.

Since mole uses these indices while importing previously saved paths, this leads to an error [Plugin: Mole] [Mole.Path] Failed to import path #1: 'MediumLevelILVarSsa' object has no attribute 'params' and the import fails.

[pdamian]

To serialize a MediumLevelILInstruction, we currently use

{
   "fun_addr": hex(inst.function.source_function.start),
   "expr_idx": inst.expr_index
}

which is not really stable (expression indices might change when working with the BinaryView).

It is currently not clear, how to make this more robust.
At least, we can do better exception handling and warn the user about potentially inconsistent paths.