RFR: 8256585: Remove in-place conversion vector operators from Vector API

[Sandhya Viswanathan]

Remove partially implemented in-place conversion vector operators from Vector API:
   ofNarrowing, ofWidening, INPLACE_XXX

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Commit messages:
 - 8256585: Remove in-place conversion vector operators from Vector API

Changes: https://git.openjdk.java.net/jdk/pull/1305/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1305&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256585
  Stats: 121 lines in 1 file changed: 0 ins; 118 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1305.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1305/head:pull/1305

PR: https://git.openjdk.java.net/jdk/pull/1305