RFR: 8355223: Improve documentation on @IntrinsicCandidate [v2]

[Chen Liang]

> In offline discussion, we noted that the documentation on this annotation does not recommend minimizing the intrinsified section and moving whatever can be done in Java to Java; thus I prepared this documentation update, to shrink a "TLDR" essay to something concise for readers, such as pointing to that list at `vmIntrinsics.hpp` instead of "a list".

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

  Refine validation and defensive copying

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24777/files
  - new: https://git.openjdk.org/jdk/pull/24777/files/6e8b3254..e8adab3c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24777&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24777&range=00-01

  Stats: 9 lines in 1 file changed: 1 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/24777.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24777/head:pull/24777

PR: https://git.openjdk.org/jdk/pull/24777