[lworld] RFR: 8369921: [lworld] Remove caches of primitive wrapper classes [v2]

[Roger Riggs]

> Disable use of wrapper cached values when --enable-preview and add javadoc descriptions for enable-preview.
> The wrapper classes are Byte, Short, Character, Integer, and Long.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Review suggestions to put constant locals into non-preview block
  and use the same code pattern for Boolean.valueOf.
  Update some tests to run in --enable-preview as well as non-preview.

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1685/files
  - new: https://git.openjdk.org/valhalla/pull/1685/files/5b7e32a8..10eab814

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1685&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1685&range=00-01

  Stats: 18 lines in 6 files changed: 15 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1685.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1685/head:pull/1685

PR: https://git.openjdk.org/valhalla/pull/1685