[jdk17u-dev] RFR: 8286800: Assert in PhaseIdealLoop::dump_real_LCA is too strong

[Goetz Lindenmaier]

I backport this for parity with 17.0.7-oracle.

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Commit messages:
 - Backport decb1b79bc475f024a02135fa3394ff97098e758

Changes: https://git.openjdk.org/jdk17u-dev/pull/1026/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1026&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286800
  Stats: 145 lines in 2 files changed: 70 ins; 40 del; 35 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1026.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/1026/head:pull/1026

PR: https://git.openjdk.org/jdk17u-dev/pull/1026