fillers: convert remaining fillers to pytest format

[danceratopz]

Convert the remaining following fillers to pytest format:

• withdrawals/withdrawals.py
• vm/dup.py
• security/selfdestruct_balance_bug.py

Experimented with a couple of new patterns for test/fixture code organization in withdrawals, in particular in TestZeroValue:

• Use an enum class to define test case names.
• Combine test case parameters in one fixture test_case_parameters that returns a dict with the aim of keeping the definition of parameters that make up a test case together.

[marioevz]

A few comments, thanks! :)