RFR: 8278863: Add method ClassDesc::ofInternalName

[Adam Sotona]

The symbolic constants API (`java.lang.constant`) was designed, in part, to provide bytecode parsing and generation APIs with a validated, common, symbolic form for constants in Java class files. 

There is an easy way to create a `ClassDesc` from a binary name (`ClassDesc::of`) or a field descriptor (`ClassDesc::ofDescriptor`) but not from an internal name. But, the internal name is common in low-level bytecode-manipulation code. 

This patch adds `ClassDesc::ofInternalName` static factory method that creates a `ClassDesc` from class internal name.
Class internal name validation and extended ClassDescTest are also parts of this patch.

CSR is linked with the issue.

Please review.

Thank you,
Adam

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Commit messages:
 - 8278863: Add method ClassDesc::ofInternalName

Changes: https://git.openjdk.org/jdk/pull/9201/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9201&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8278863
  Stats: 52 lines in 3 files changed: 52 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9201.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9201/head:pull/9201

PR: https://git.openjdk.org/jdk/pull/9201