RFR: 8362979: C2 fails with unexpected node in SuperWord truncation: CmpLTMask, RoundF

[Jasmine Karthikeyan]

Hi all,
This is a fix for a debug assert failure in SuperWord truncation for `CmpLTMask` and `RoundF` nodes, as discovered by CTW in the linked JBS report. I've added the nodes to the switch, and added reduced test cases. I've made a similar fix for `RoundD` nodes as well. Thanks!

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Commit messages:
 - Fix truncation assert for CmpLTMask and rounding

Changes: https://git.openjdk.org/jdk/pull/26494/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26494&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8362979
  Stats: 57 lines in 3 files changed: 57 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26494.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26494/head:pull/26494

PR: https://git.openjdk.org/jdk/pull/26494