RFR: 8272096: Exceptions::new_exception can return wrong exception

[Coleen Phillimore]

I added an assert if Exceptions::new_exception is called with a pending exception and fixed the places where it is called with a pending exception.   That leaves only two possible exceptions. I left the product mode code in to return the pending exception if allocating the exception message doesn't thrown OOM because it was always there and seems dubious.  Tested with jck tests and tier1-7.

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Commit messages:
 - 8272096: Exceptions::new_exception can return wrong exception

Changes: https://git.openjdk.org/jdk/pull/9492/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9492&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8272096
  Stats: 29 lines in 4 files changed: 7 ins; 5 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/9492.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9492/head:pull/9492

PR: https://git.openjdk.org/jdk/pull/9492