* When constructing instructions which have substitution maps: initialize those with the canonical SubstitutionMap
* Also initialize SILFunction::ForwardingSubMap with the canonical one
Non-canonical substitution maps may prevent generic specializations.
This fixes a problem in Embedded Swift where an error is given because a function cannot be specialized, although it should.
https://github.com/swiftlang/swift/issues/83895
rdar://159065157
