Fix async JNI strict concurrency

[nerzh]

Problem found:

Swift Java generated JNI wrappers for async Swift functions no longer compile with newer Swift strict concurrency checks. The generated Task closures capture JNI values and temporary Swift conversion values that are not Sendable, so Swift reports data-race risk errors during compilation.

How it was fixed:

I added an unchecked Sendable wrapper for values that must cross into the generated async Task body. The generator now tracks, structurally, which temporary values are created during JNI-to-Swift parameter conversion and wraps only those values before creating the task. Inside the task, the original values are restored from the wrapper and used as before.

This avoids fragile string parsing of generated Swift code and keeps the fix limited to async JNI generation. Existing async JNI tests were updated to match the new generated output.

[ktoso]

Hi thanks for the PR, I’m on holiday so unable to review deeply here this week.

im worried about unsafe wrappers like this, and would like to explore other options