RFR: 8256401: ZGC: Improve ZList verification [v3]

[Per Liden]

> The ZList verification is currently fairly weak. I propose that we make the verification stronger to easier detect corrupt lists and misuse of list nodes. This patch also removes the unused `ZList::transfer()` function.

Per Liden has updated the pull request incrementally with one additional commit since the last revision:

  Review 1

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1230/files
  - new: https://git.openjdk.java.net/jdk/pull/1230/files/20a9314b..c8d25093

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1230&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1230&range=01-02

  Stats: 2 lines in 2 files changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1230.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1230/head:pull/1230

PR: https://git.openjdk.java.net/jdk/pull/1230