RFR: 8282053: IGV: refine schedule approximation

[Daniel Skantz]

This patch refines the schedule approximation in IGV by 1)  placing parm. and projection nodes in the same block as their predecessors, and 2) disallows erroneously considering machine nodes such as prefetchAlloc and rep_stos as CFG nodes.

The reader may refer to the corresponding JBS issue where graphs sampled before and after the change are attached.

Testing: T1-T3 with no failures. Opened graphs before and after the change and saw no obvious problems. Opened a large number of graphs in CFG view and observed no unexpected IGV warnings, errors or assert failures.

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Commit messages:
 - fix

Changes: https://git.openjdk.org/jdk/pull/24350/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24350&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282053
  Stats: 21 lines in 1 file changed: 20 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24350.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24350/head:pull/24350

PR: https://git.openjdk.org/jdk/pull/24350