RFR: 8294982: Implementation of Classfile API

[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/jdk/classfile/package-summary.html) is also available.

Please take you time to review this non-trivial JDK addition.

Thank you,
Adam

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Commit messages:
 - removed executable
 - removed executable
 - removed executable flags and fixed whitespaces
 - removed executable flag from test/micro/org/openjdk/bench/jdk/classfile/Write.java
 - Merge branch 'classfile-api-branch' into classfile-api-initial-branch
 - Merge branch 'master' into classfile-api-branch
 - fixed Classfile API Javadoc build
 - removed obsolete factory mthods LocalVariableInfo::of and LocalVariableTypeInfo::of
 - added Classfile.Option FILTER_DEAD_LABELS
 - fixed javadoc of ModuleOpenInfo and ModuleRequireInfo
 - ... and 85 more: https://git.openjdk.org/jdk/compare/8ee0f7d5...4b3e63d5

Changes: https://git.openjdk.org/jdk/pull/10982/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10982&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294982
  Stats: 53247 lines in 322 files changed: 53246 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