spirv-fuzz: Add all opcodes that are agnostic to signedness of operands to function

The function IsAgnosticToSignednessOfOperand of
TransformationReplaceIdWithSynonym returns true when the given
opcode is agnostic to the signedness of the operand at the
given index.

The function only recognises some of such opcodes and it should
be completed so that it includes all of the opcodes satisfying the
requirement.

Start at IsAgnosticToSignednessOfOperand in TransformationReplaceIdWithSynonym and review the opcode cases it currently recognizes. Compare them with the full set of signedness-agnostic operand opcodes, then verify that every qualifying opcode is handled consistently; the function should return true for all such opcode and operand-index combinations.

Written by the indexing model from the issue text.