RFR: 7439: Introduced IConstantPoolExtension for Constant Pools [v4]

[Jean-Philippe Bempel]

> Add extension methods when constants are read, referenced, resolved, constant pools fully resolved and parsing finished to be able for example:
> 
>  * track constant pool usage inside events
>  * replace or translate symbols, method names, etc... like
> de-obfuscations of stack traces

Jean-Philippe Bempel has updated the pull request incrementally with one additional commit since the last revision:

  added new extension methods
  
  - getId
  - eventsLoaded
  - getItemCollection to expose data gathered
  
  and exposed in IParserStats all ConstantPool extensions

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Changes:
  - all: https://git.openjdk.java.net/jmc/pull/333/files
  - new: https://git.openjdk.java.net/jmc/pull/333/files/ff798074..33732c9a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=333&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=333&range=02-03

  Stats: 92 lines in 8 files changed: 70 ins; 15 del; 7 mod
  Patch: https://git.openjdk.java.net/jmc/pull/333.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/333/head:pull/333

PR: https://git.openjdk.java.net/jmc/pull/333