RFR: 8200559: Java agents doing instrumentation need a means to define auxilary classes [v2]

[Rafael Winterhalter]

> To allow agents the definition of auxiliary classes, an API is needed to allow this. Currently, this is often achieved by using `sun.misc.Unsafe` or `jdk.internal.misc.Unsafe` ever since the `defineClass` method was removed from `sun.misc.Unsafe`.

Rafael Winterhalter has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8200559: Java agents doing instrumentation need a means to define auxiliary classes

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3546/files
  - new: https://git.openjdk.java.net/jdk/pull/3546/files/362efc82..2ef21598

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3546&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3546&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3546.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3546/head:pull/3546

PR: https://git.openjdk.java.net/jdk/pull/3546