[master] RFR: Fix use of Klass* in GC JFR reporting [v3]

[Roman Kennke]

> Some JFR related code paths in GC access the Klass* of old objects that has already been overidden by the forwarding pointer. We can easily use the Klass* that we fetched earlier instead.
> 
> Testing:
>  - [x] tier1
>  - [x] tier2
>  - [x] jdk/jfr (some of which still fails, see subsequent PRs)

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Whitespace fixes

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Changes:
  - all: https://git.openjdk.java.net/lilliput/pull/17/files
  - new: https://git.openjdk.java.net/lilliput/pull/17/files/ce81fbf9..5286943e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=lilliput&pr=17&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=lilliput&pr=17&range=01-02

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/lilliput/pull/17.diff
  Fetch: git fetch https://git.openjdk.java.net/lilliput pull/17/head:pull/17

PR: https://git.openjdk.java.net/lilliput/pull/17