RFR: 8330106: C2: VectorInsertNode::make() shouldn't call ConINode::make() directly

[Roland Westrelin]

This is a minor issue that I ran into at some point with JDK-8275202:
calling `PhaseValues::intcon()` is required so the node is properly
entered in the GVN's hash table and its type is properly recorded in
the GVN's type table.

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Commit messages:
 - fix

Changes: https://git.openjdk.org/jdk/pull/18742/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18742&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330106
  Stats: 4 lines in 3 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/18742.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18742/head:pull/18742

PR: https://git.openjdk.org/jdk/pull/18742