AMDGPU/GlobalISel/Emitter Support for predicate code that uses operands

Predicates with 'let PredicateCodeUsesOperands = 1' want to examine
matched operands. When we encounter predicate code that uses operands,
analyze its named operand arguments and create a map between argument
index and name. Later, when leaf node with name is encountered, emit
GIM_RecordNamedOperand that will store that operand at its argument
index in operand list. This operand list will be an argument to c++
code of the predicate.

Differential Revision: https://reviews.llvm.org/D87285