RFR: 8361300: Document exceptions for Unsafe offset methods [v4]

[Chen Liang]

> Unsafe throws IAE for misusing static vs instance fields, and it's revealed that AtomicXxxFieldUpdaters are using this mechanism to reject static fields. This is not a good practice, but we can at least document this so we don't accidentally introduce problems.

Chen Liang has updated the pull request incrementally with one additional commit since the last revision:

  Test to verify observed internal unsafe behaviors

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25945/files
  - new: https://git.openjdk.org/jdk/pull/25945/files/c8fcf03c..57f863b7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25945&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25945&range=02-03

  Stats: 102 lines in 1 file changed: 102 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25945.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25945/head:pull/25945

PR: https://git.openjdk.org/jdk/pull/25945