Fix AsyncStream release JNI binding

[michele-theleftbit]

Fixes #50.

Adds stable @JvmName("Swift_release") directives for both AsyncStreamSwiftDataSource and AsyncThrowingStreamSwiftDataSource, matching Swift_next and preventing Kotlin from looking up the mangled Swift_release$SkipLib JNI symbol.

Validation:

• Reviewed the generated Android binding and the two-line source diff.
• swift test was not run locally.

AI was used to help investigate the generated binding and prepare this focused change; I manually reviewed the final diff.

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[marcprux]

Perfect, thanks!