Fixes#4170, by checking the signedness of bitwise operands in
TransformationAddBitInstructionSynonym, to avoid an "Expected Base
Type to be equal to Result Type" validation error.
Adds some functions that allow a fuzzer pass to check whether it is
spiralling out of control and exit early. The fuzzer pass for adding
bit instruction synonyms now uses this. Also make many methods in
FuzzerContext const.
This PR implements part of the add bit instruction synonym transformation.
For now, the implementation covers the OpBitwiseOr, OpBitwiseXor and
OpBitwiseAnd cases.
