swift234

[SE-0095] [Runtime], [Demangler], & AST printer updated to new composition syntax

- All parts of the compiler now use ‘P1 & P2’ syntax
- The demangler and AST printer wrap the composition in parens if it is
in a metatype lookup
- IRGen mangles compositions differently
    - “protocol<>” is now “swift.Any”
    - “protocol<_TP1P,_TP1Q>” is now “_TP1P&_TP1Q”
- Tests cases are updated and added to test the new syntax and mangling