RFR: 8265129: Add intrinsic support for JVM.getClassId [v2]

[Denghui Dong]

> 8265129: Add intrinsic support for JVM.getClassId

Denghui Dong has updated the pull request incrementally with one additional commit since the last revision:

  add doc

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3470/files
  - new: https://git.openjdk.java.net/jdk/pull/3470/files/1a429be3..8315bffd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3470&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3470&range=00-01

  Stats: 17 lines in 1 file changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3470.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3470/head:pull/3470

PR: https://git.openjdk.java.net/jdk/pull/3470