Fix crash when Any type parsing

[sidepelican]

When reading the following code causes the jextract command to crash.

public func f() -> Any {
    return 0
}

JExtractSwiftLib/SwiftType.swift:368: Fatal error: Unexpectedly found nil while unwrapping an Optional value

According to swift-syntax, Any is not an Identifier and thus cannot be handled by the lookup.

https://github.com/swiftlang/swift-syntax/blob/65b02a90ad2cc213e09309faeb7f6909e0a8577a/Sources/SwiftSyntax/Identifier.swift#L31

Since Any is existential, neither JNI mode nor FFM mode is currently supported. Therefore, I'll modify the implementation to simply ignore it.

[sidepelican]

Ah, I've discovered that existentials in argument position are supported in JNI mode.
I need to reconsider how Any should be represented.

[ktoso]

Edit with more ideas: I guess we'd have to defensively copy into a new buffer since we don't know if the value is a value or an instance to retain... that'd force us into arena use as well (tho in JNI i guess going global by defalt may be fine).

It's a tricky question, ok to leave as is for now

[sidepelican]

Implementing full support for Any seems take a time.
My main focus is to avoid the fatal error, so I’d like to handle Any as unsupported.

[ktoso]

Yeah that works for me, thanks

[ktoso]

Whoops misclicked, tests passed