[master] RFR: 8308900: [Lilliput] Cherry-pick C2 prototype header improvements

[Aleksey Shipilev]

This cherry-picks the commit from the upstream review: https://github.com/rkennke/jdk/commit/3a18945ce900e229331b1412002da4a6965e0764.

It also fixes the affected code with more `UseCompactObjectHeaders` guards, and partially reverts it to upstream state.

Additional testing:
 - [ ] Linux x86_64 fastdebug `tier1`
 - [ ] Linux x86_64 fastdebug `tier1` + `+UseCompactObjectHeaders`

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Commit messages:
 - Cleaner upstream reversal
 - Cherry-pick C2 prototype header improvements

Changes: https://git.openjdk.org/lilliput/pull/95/files
 Webrev: https://webrevs.openjdk.org/?repo=lilliput&pr=95&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308900
  Stats: 51 lines in 5 files changed: 47 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/lilliput/pull/95.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/95/head:pull/95

PR: https://git.openjdk.org/lilliput/pull/95