RFR: 8294982: Implementation of Classfile API [v20]

[Adam Sotona]

> This is root pull request with Classfile API implementation, tests and benchmarks initial drop into JDK.
> 
> Following pull requests consolidating JDK class files parsing, generating, and transforming ([JDK-8294957](https://bugs.openjdk.org/browse/JDK-8294957)) will chain to this one.
> 
> Classfile API development is tracked at:
> https://github.com/openjdk/jdk-sandbox/tree/classfile-api-branch
> 
> Development branch of consolidated JDK class files parsing, generating, and transforming is at:
> https://github.com/openjdk/jdk-sandbox/tree/classfile-api-dev-branch
> 
> Classfile API [JEP](https://bugs.openjdk.org/browse/JDK-8280389) and [online API documentation](https://htmlpreview.github.io/?https://raw.githubusercontent.com/openjdk/jdk-sandbox/classfile-api-javadoc-branch/doc/classfile-api/javadoc/java.base/jdk/internal/classfile/package-summary.html) is also available.
> 
> Please take you time to review this non-trivial JDK addition.
> 
> Thank you,
> Adam

Adam Sotona has updated the pull request incrementally with one additional commit since the last revision:

  added 4-byte Unicode text to Utf8EntryTest

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10982/files
  - new: https://git.openjdk.org/jdk/pull/10982/files/dbb9e46a..7a45ebd3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10982&range=19
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10982&range=18-19

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10982.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10982/head:pull/10982

PR: https://git.openjdk.org/jdk/pull/10982