RFR: 8350983: JShell LocalExecutionControl only needs stopCheck() on backward branches [v3]

[Archie Cobbs]

> JShell's `LocalExecutionControl` ensures a running eval thread can be stopped by `JShell.stop()` by inserting an invocation of `stopCheck()` at every branch point in the bytecode of loaded classfiles.
> 
> However, this same guarantee can be provided by invoking `stopCheck()` only at backward branches and not at forward branches. By doing this, the performance and size impact on the executing code can be reduced.
> 
> Fortunately the new ClassFile API makes this kind of modification easy 👍

Archie Cobbs has updated the pull request incrementally with one additional commit since the last revision:

  Style improvements based on review comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23850/files
  - new: https://git.openjdk.org/jdk/pull/23850/files/30c5f1a3..16a39b28

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23850&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23850&range=01-02

  Stats: 6 lines in 1 file changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/23850.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23850/head:pull/23850

PR: https://git.openjdk.org/jdk/pull/23850