RFR: 8341483: Clarify special case handling of Types.getArrayType [v2]

[Joe Darcy]

> Add specification and tests for invalid inputs to getArrayType that generation an exception. As initially written, this PR changes the behavior on NONE and the null type.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Respond to review feedback.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21346/files
  - new: https://git.openjdk.org/jdk/pull/21346/files/222cfa97..c016fb63

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21346&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21346&range=00-01

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21346.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21346/head:pull/21346

PR: https://git.openjdk.org/jdk/pull/21346