RFR: First refactoring (thaw_fast) [v6]

[Frederic Parain]

> Refactoring method thaw_fast() for better encapsulation and readability.

Frederic Parain has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge remote-tracking branch 'upstream/fibers' into renaming1
 - Re-order methods
 - Merge remote-tracking branch 'upstream/fibers' into renaming1
 - Merge remote-tracking branch 'upstream/fibers' into renaming1
 - Move new methods to ThawBase
 - Fixes to address Coleen's comments.
 - First refactoring (thaw_fast)

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Changes: https://git.openjdk.java.net/loom/pull/158/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=158&range=05
  Stats: 211 lines in 9 files changed: 98 ins; 60 del; 53 mod
  Patch: https://git.openjdk.java.net/loom/pull/158.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/158/head:pull/158

PR: https://git.openjdk.java.net/loom/pull/158