RFR: 8361300: Document exceptions for Unsafe offset methods [v5]

[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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Move exception to Java code, stress the field must be known
 - Merge branch 'master' of https://github.com/openjdk/jdk into doc/unsafe-field-offset
 - Test to verify observed internal unsafe behaviors
 - Add tck coverage
 - Explicit static checks
 - Simplify
 - Add static check
 - Document IAE for Unsafe offset methods

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25945/files
  - new: https://git.openjdk.org/jdk/pull/25945/files/57f863b7..71584eb3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25945&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25945&range=03-04

  Stats: 67725 lines in 1877 files changed: 38128 ins; 19192 del; 10405 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