Now `Optional` conforms to `_BridgedSwiftStackType` whenever `Wrapped`
conforms to `_BridgedSwiftStackType`. This makes generic programming
easier and reduces boilerplate in intrinsics and codegen.

For specialized handling of certain types like associated value enums,
where the presence of a value is encoded as a sentinel case ID (-1),
we implement `bridgeJSStack{Push,Pop}AsOptional` methods, which is on
the witness table of `_BridgedSwiftStackType`.

Also now some of optional types no longer pushes placeholders values for
`nil` cases when pushing in JS and popping in Swift.

…9941ebaf3ac11

BridgeJS: Remove inline array lifting/lowering codegen

BridgeJS: Cover more Array cases in runtime tests

…#679)

BridgeJS: Move out default argument tests into a separate suite

…f174d13f79b1a

…ace-nested classes

…odegen

BridgeJS: Fix property codegen using unqualified type name for namespace-nested classes

…classes and structs

…061feae89f16f

BridgeJS: Remove `_BridgedSwiftDictionaryStackType` protocol

BridgeJS: Include namespace prefix in ABI names for namespace-nested classes and structs