RFR: 8322694: C1: Handle Constant and IfOp in NullCheckEliminator

[Denghui Dong]

This patch added the support for Constant and IfOn in NullCheckEliminator to eliminate more null check.

testing: tier1-4 in progress

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Commit messages:
 - 8322694: C1: Handle Constant and IfOp in NullCheckEliminator

Changes: https://git.openjdk.org/jdk/pull/17191/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17191&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322694
  Stats: 28 lines in 1 file changed: 25 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/17191.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17191/head:pull/17191

PR: https://git.openjdk.org/jdk/pull/17191