RFR: 8275586: Zero: Simplify interpreter initialization

[Aleksey Shipilev]

The prolog in `BytecodeInterpreter` is hairy due to early initialization of interpreter statics. Previous rewrites make it mostly redundant, and we can now simplify it.

This also implicitly fixes a initialization bug. If `JvmtiExport::can_post_interpreter_events()` changes at runtime, we will call into the uninitialized version:


    // Call the interpreter
    if (JvmtiExport::can_post_interpreter_events()) {
      BytecodeInterpreter::run<true>(istate);
    } else {
      BytecodeInterpreter::run<false>(istate);
    } 


Additional testing:
 - [ ] Linux x86_64 fastdebug `make bootcycle-images`

-------------

Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/6029/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6029&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275586
  Stats: 70 lines in 3 files changed: 7 ins; 48 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6029.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6029/head:pull/6029

PR: https://git.openjdk.java.net/jdk/pull/6029