RFR: 6890: defineEventProbes should throw exception on malformed probe definitions [v2]

[Joshua Matsuoka]

> This PR addresses JMC-6890 (defineEventProbes should throw exception on malformed probe definitions) [1]. Previously the exception would be swallowed by DefaultTransformRegistry when the XML failed validation, and would simply return null. With this change the exception is rethrown and can be handled accordingly by the AgentController, which rethrows it, and the user. I've added a test for the AgentController and updated the test for DefaultTransformRegistry accordingly.
> 
> [1] https://bugs.openjdk.java.net/browse/JMC-6890

Joshua Matsuoka has updated the pull request incrementally with one additional commit since the last revision:

  Update Copyright headers, have XML validation throw its' own exception

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Changes:
  - all: https://git.openjdk.java.net/jmc/pull/227/files
  - new: https://git.openjdk.java.net/jmc/pull/227/files/b563856e..5c6c695a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=227&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=227&range=00-01

  Stats: 120 lines in 10 files changed: 70 ins; 3 del; 47 mod
  Patch: https://git.openjdk.java.net/jmc/pull/227.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/227/head:pull/227

PR: https://git.openjdk.java.net/jmc/pull/227