JFR: Rewrite instrumentation to use Class-File API

Today, the ASM framework dynamically generates bytecode to commit events into thread local buffers. Plan is to modify the code generation process to enable user-defined events to selectively opt-out of event thread, stack trace, and duration fields. JVM events already have this capability.

Before doing the bytecode generation changes, it make sense to rewrite it using the new Class-File API. This minimizes necessary code modifications and simplifies the implementation of the opt-out mechanism.