RFR: 8306842: Classfile API performance improvements [v9]

[Adam Sotona]

> Following improvements implemented:
> - Switch over `String` replaced with switch single char
> - Binary search for frames in `StackMapGenerator`
> - `StackMapGenerator.rawHandlers` with pre-calculated offsets
> - `ClassEntry` is caching `ClassDesc` symbol
> - Caching of type symbols in `NameAndTypeEntry` and `MethodTypeEntry`
> - Caching `MethodTypeDesc` in `MethodInfo` implementations
> - `StackMapGenerator` and `Utils` delegating to cached `MethodTypeDesc` instead of custom parsing
> 
> No API change.
> 
> Benchmarks show stack map generation improved by 21% and code generation from symbols improved by 30%.
> 
> 
> Benchmark                     Mode  Cnt       Score       Error  Units
> GenerateStackMaps.benchmark  thrpt   10  407931.202 ± 13101.023  ops/s
> RebuildMethodBodies.shared   thrpt    4   10258.597 ±   383.699  ops/s
> RebuildMethodBodies.unshared thrpt    4    7224.543 ±   256.800  ops/s
> 
> 
> 
> Benchmark                     Mode  Cnt       Score      Error  Units
> GenerateStackMaps.benchmark  thrpt   10  495101.110 ± 2389.628  ops/s
> RebuildMethodBodies.shared    thrpt   4   13380.272 ±  810.113  ops/s
> RebuildMethodBodies.unshared  thrpt   4    9399.863 ±  557.060  ops/s

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

  removed obsolete exports

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13671/files
  - new: https://git.openjdk.org/jdk/pull/13671/files/d99e7ad0..07079387

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13671&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13671&range=07-08

  Stats: 3 lines in 3 files changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13671.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13671/head:pull/13671

PR: https://git.openjdk.org/jdk/pull/13671