RFR: 8261031: Move some ClassLoader name checking to native/VM [v3]

[Claes Redestad]

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

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Consolidate verifyClassname and verifyFixClassname

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2378/files
  - new: https://git.openjdk.java.net/jdk/pull/2378/files/727b2b37..6b8305e9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2378&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2378&range=01-02

  Stats: 77 lines in 4 files changed: 13 ins; 40 del; 24 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