RFR: 8361699: C2: assert(can_reduce_phi(n->as_Phi())) failed: Sanity: previous reducible Phi is no longer reducible before SUT.

[Cesar Soares Lucas]

Please, review this patch to fix issue that may occur when reducing allocation merge.

As the assert message describe, the problem is a `Phi` considered reducible during one invocation of  `adjust_scalar_replaceable_state` turned out to be later non-reducible. This situation can happen if a subsequent invocation of the same method causes all inputs to the phi to be NSR; therefore there is no point in reducing the Phi. It can also happen during the propagation of NSR state done by `find_scalar_replaceable_allocs`. 

The change in `revisit_reducible_phi_status` is just a clean-up.
The real fix is in `find_scalar_replaceable_allocs`.

Tested on Linux x64/Aarch64 release/fastdebug with JTREG tier1-3.

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Commit messages:
 - Fix for RAM not reducible before SUT & Test.

Changes: https://git.openjdk.org/jdk/pull/27063/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27063&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361699
  Stats: 87 lines in 2 files changed: 73 ins; 13 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27063.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27063/head:pull/27063

PR: https://git.openjdk.org/jdk/pull/27063