RFR: 8335977: Deoptimization fails with assert "object should be reallocated already"

[Cesar Soares Lucas]

Please, review this patch to fix an issue that may occur when serializing debug information related to reduce allocation merges. The problem happens when there are more than one JVMS in a `uncommon_trap` and a _younger_ JVMS doesn't have the RAM inputs as a local/expression/monitor but an older JVMS does. In that situation the loop at line 1173 of output.cpp will set the `is_root` property of the ObjectValue to `false` when processing the younger JVMS even though it may have been set to `true` when visiting the older JVMS.

Tested on: 
 - Win, Mac & Linux tier1-4 on x64 & Aarch64.
 - CTW with some thousands of jars.

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Commit messages:
 - Preserve is_root status across JVMS.

Changes: https://git.openjdk.org/jdk/pull/21624/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21624&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335977
  Stats: 102 lines in 2 files changed: 100 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21624.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21624/head:pull/21624

PR: https://git.openjdk.org/jdk/pull/21624