RFR: 8359707: Add classfile modification code to RedefineClassHelper [v9]

[Coleen Phillimore]

> I copied this code for another test in the Valhalla repo and thought it would be a good utility function.  It might be better written using the Classfile API.
> Tested with test.

Coleen Phillimore has updated the pull request incrementally with two additional commits since the last revision:

 - Update test/lib/RedefineClassHelper.java
   
   Co-authored-by: David Holmes <62092539+dholmes-ora at users.noreply.github.com>
 - Update test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/ClassVersionAfterRedefine.java
   
   Co-authored-by: David Holmes <62092539+dholmes-ora at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25857/files
  - new: https://git.openjdk.org/jdk/pull/25857/files/17b3b77b..8f360d65

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25857&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25857&range=07-08

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25857.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25857/head:pull/25857

PR: https://git.openjdk.org/jdk/pull/25857