RFR: 6936: Parser should track statistics during parsing

[Jean-Philippe Bempel]

Add new `IParserStats` interface implemented by `EventCollection`.
That way, `IItemCollection` is not touched, but you need to cast the
instance to `IParserStats`.
Support of old (v0.x) JFR format.
During parsing, we collect number of events per type, the size, number
of chunks and version of the file.
We also track for version 1.x/2.x the number of skipped events.
`RecordingPrinter` tool class is modified to support a summary verbosity mode
and `-summary` option to print statistics per event type.

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Commit messages:
 - 6936: Parser should track statistics during parsing

Changes: https://git.openjdk.java.net/jmc/pull/219/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=219&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6936
  Stats: 414 lines in 22 files changed: 400 ins; 0 del; 14 mod
  Patch: https://git.openjdk.java.net/jmc/pull/219.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/219/head:pull/219

PR: https://git.openjdk.java.net/jmc/pull/219