[lworld] RFR: 8353236: [lworld] Better documentation for Valhalla Unsafe intrinsics [v3]

[Quan Anh Mai]

> Hi,
> 
> This patch clarifies the meaning of undefined behavior when working with `Unsafe` and specifies the requirements when working with `Unsafe::makePrivateBuffer` and `Unsafe::finishPrivateBuffer`.
> 
> Please take a look and leave your suggestions, thanks a lot.

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  remove unnecessary statements

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1425/files
  - new: https://git.openjdk.org/valhalla/pull/1425/files/b869e10c..130f897f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1425&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1425&range=01-02

  Stats: 4 lines in 1 file changed: 1 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1425.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1425/head:pull/1425

PR: https://git.openjdk.org/valhalla/pull/1425