[JExtract/JNI] Add auto arena to SwiftKitCore and add memory management options

[madsodgaard]

Since java.lang.ref.Cleaner is not available in Android (before API 33), we introduce our own Cleaner which is very similar to the original JDK implementation, but a few simplications for our use case. This allows us to introduce the Auto arena to the JNI mode through SwiftArena.ofAuto().

Note: The SwiftKitFFM still uses the JDK Cleaner, this is only for the JNI/SwiftKitCore library.

In an ideal world we would somehow differentiate between users needing to support Android (use our own) and people just running on regular JVM (then we use the original Cleaner) - perhaps that is something we could look into in the future, by providing an Android "compatibility" library of SwiftKitCore.

On top of that we introduce a new "memory management mode". This mode can be specified using --memory-management-mode and has the following options:

• explicit (default): Generates only wrappers that require explicit passing of SwifttArena
• allow-global-automatic: Generates wrappers that use a default global auto arena, but also explicit APIs.

This option is only supported in JNI for now.

Resolves #318

[ktoso]

Pretty good, I think that'd be okey -- some comments inline.

I remain unclear about which android versions don't / do have this, so that may be worth double checking before we commit our own cleaner like things but we could do this if we need to.

[madsodgaard]

@ktoso It was first added in API level 33: https://developer.android.com/reference/java/lang/ref/Cleaner

[ktoso]

I see, and we're trying to support 28/29+ I guess... Let's take this then