RFR: 8340571: Outline code from the loop in ZipFile.Source.initCen

[Claes Redestad]

This PR suggests refactoring `ZipFile.Source.initCEN` to move as much logic as possible into the per-entry method processor. This inner method will be called often and JIT optimized earlier in the bootstrap sequence.

Startup tests using the OpenJDK benchmarks.jar show a ~1ms improvement on both my M1 macbook and my x64 wokstation, while we also improve on relevant throughput microbenchmarks:


Name               (size) Cnt       Base      Error        Test      Error  Unit  Change
openCloseZipFile      512  15  61372.449 ± 1197.432   58081.423 ± 1751.988 ns/op   1.06x (p = 0.000*)
openCloseZipFile     1024  15 117953.727 ± 3202.274  112548.875 ± 5126.665 ns/op   1.05x (p = 0.001*)
openCloseZipFilex2    512  15  62141.795 ±  674.121   60520.017 ± 2438.346 ns/op   1.03x (p = 0.017 )
openCloseZipFilex2   1024  15 117959.071 ± 1528.426  111773.937 ± 1604.412 ns/op   1.06x (p = 0.000*)
  * = significant

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Commit messages:
 - Further tuning, avoid unnecessary long conversions
 - Fix after merge
 - Merge optimization rework
 - Cleanup, further micro-optimization
 - Extract a state object and call that in a loop, shifting work from initCEN to checkAndAddEntry
 - Use zero as ZIP_ENDCHAIN marker to avoid the Arrays.fill
 - Avoid loading TreeSet
 - Going all the way
 - merge master
 - Use zero as ZIP_ENDCHAIN marker to avoid the Arrays.fill
 - ... and 5 more: https://git.openjdk.org/jdk/compare/ab06a878...19f33b8b

Changes: https://git.openjdk.org/jdk/pull/21133/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21133&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340571
  Stats: 152 lines in 2 files changed: 65 ins; 47 del; 40 mod
  Patch: https://git.openjdk.org/jdk/pull/21133.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21133/head:pull/21133

PR: https://git.openjdk.org/jdk/pull/21133