[Tests] SSZ unsigned integer + test suite genericity

[mratsim]

Adds the unsigned int official fixtures of SSZ to the test suite.
This also revamp the test suite to be generic over presets and the test cases following status-im/nim-serialization#4 and status-im/nim-serialization#5 (upstream bug nim-lang/Nim#11225)

In details this PR does the following

• Genericity

  • Now a single parseTests that accepts test types is defined
  • Test types have been moved to their test files instead of fixture_utils.nim

• SSZ uint tests added except

  • skipped uint128 and uint256
  • "wrong length" tests skipped due to [SSZ] Decoding does not fail if the byte sequence overflows the destination type #280
  • skipped overflow tests, they do not throw an exception
  • underflow tests correctly throws an exception though

[mratsim]

When I compile the file test_fixture_ssz_uint.nim file alone and run it, test is OK, when run in the full test suite the unittest expect template throws:

Expect Failed, unexpected exception was thrown.

Edit: it was an AssertionError that was thrown in stint, raised status-im/nim-stint#79 to use a single RangeError in the future

[mratsim]

Not sure about the windows 64-bit only "Access is denied" error.