RFR: 8261031: Move some ClassLoader name checking to native/VM

[Claes Redestad]

This patch moves some sanity checking done in ClassLoader.java to the corresponding endpoints in native or VM code.

-------------

Commit messages:
 - Copyrights
 - Move class name checking for findBootstrapClass/findLoadedClass into native/VM

Changes: https://git.openjdk.java.net/jdk/pull/2378/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2378&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261031
  Stats: 20 lines in 3 files changed: 11 ins; 4 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2378.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2378/head:pull/2378

PR: https://git.openjdk.java.net/jdk/pull/2378