[master] RFR: 8300527: [Lilliput] Simplify and optimize loading of Klass* [v2]

[Roman Kennke]

> With the new fast-locking, we can greatly simplify the loading of the Klass* from an object. We no longer have to call into the runtime to ensure that the header is changed under our feet (by installing the INFLATION marker). Instead, we can do a simple check for the object being monitor-locked, and safely load the displaced header, if that is the case.

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

  Use _stub instead of stub()

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Changes:
  - all: https://git.openjdk.org/lilliput/pull/66/files
  - new: https://git.openjdk.org/lilliput/pull/66/files/83c65c16..fcff6601

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=66&range=01
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=66&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/lilliput/pull/66.diff
  Fetch: git fetch https://git.openjdk.org/lilliput pull/66/head:pull/66

PR: https://git.openjdk.org/lilliput/pull/66