Fix boolean primitive field accessor

[KingParmenides]

Summary

• read instance boolean primitive kernel fields with the JNI boolean signature/accessor
• keep byte primitive handling on the existing byte path

Addresses Syncleus/aparapi#91.

Validation

• git diff --check -- src/cpp/runKernel/KernelArg.cpp
• inspected the matching static boolean path, which already uses Z and GetStaticBooleanField

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