When generating Rust code for an instruction predicate, call the corresponding
function in the predicates module, using a qualified name.
We don't have methods corresponding to the predicates.
This collects all of the leaf predicates that go into a compound predicate.
Current leaf predicates are:
- Settings for ISA predicates, and
- FieldPredicates for instruction predicates.
Add new instruction predicates to support the 'I' encoding recipe: IsSignedInt,
IsUnsignedInt used to test that an immediate operand is in the allowed range.
Predcates are boolean functions. There will be ISA predicates and instruction
predicates.
The ISA predicates will be turned into member functions on the generated Flags
structs.
