RFR: 8345485: C2 MergeLoads: merge adjacent array/native memory loads into larger load

[kuaiwei]

WIP.

It worked for cases in the TestMergeLoads.java and can observe performance improvement in MergeLoadBench.getIntB . Need to check more cases.

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Commit messages:
 - Remove some debug trace
 - 8345485: C2 MergeLoads: merge adjacent array/native memory loads into larger load

Changes: https://git.openjdk.org/jdk/pull/24023/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24023&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345485
  Stats: 957 lines in 14 files changed: 911 ins; 0 del; 46 mod
  Patch: https://git.openjdk.org/jdk/pull/24023.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24023/head:pull/24023

PR: https://git.openjdk.org/jdk/pull/24023