If possible, add imported members to the StructDecl's LookupTable rather than adding them directly as members. This will fix the issues with ordering that #39436 poorly attempted to solve during IRGen.
This also allows us to break out most of the test changes from #39436.
Simply treat scoped enums as (pre-existing) "non frozen enums". C++
scoped enums are actually imported as Swift enums (unlike other enums)
and no global variables need be created (given their "scoped" nature).
This is a small fix to prevent a crash. This change simply adds another
condition for the "bool" branch that checks if "type" is associated with
a "clang::EnumDecl" with an underlying type of "bool", and if so, treats
"type" as a "Bool".
