RFR: 8340132: Remove internal CpException for reading malformed utf8

[Chen Liang]

Remove an internal exception for invalid utf8 entry format; it should have been an IllegalArgumentException but was an arbitrary subtype of RuntimeException. Converted to throw ConstantPoolException, and consolidated into a single method to reduce code size.

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

Commit messages:
 - 8340132: Remove internal CpException for reading malformed utf8

Changes: https://git.openjdk.org/jdk/pull/21027/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21027&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340132
  Stats: 17 lines in 1 file changed: 4 ins; 8 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/21027.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21027/head:pull/21027

PR: https://git.openjdk.org/jdk/pull/21027