RFR: 8266189: Remove C1 "IfInstanceOf" instruction

[Yi Yang]

Remove IfInstanceOf instruction, it has been there for a long while(13yrs) and not implemented yet.

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Commit messages:
 - remove c1 IfInstanceOf

Changes: https://git.openjdk.java.net/jdk/pull/3935/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3935&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266189
  Stats: 93 lines in 10 files changed: 0 ins; 93 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3935.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3935/head:pull/3935

PR: https://git.openjdk.java.net/jdk/pull/3935