RFR: 6669: FlameGraphView tree calculation should (probably) be interruptable [v3]

[Miroslav Wengner]

> fix to bug: https://bugs.openjdk.java.net/browse/JMC-6669

Miroslav Wengner has updated the pull request incrementally with one additional commit since the last revision:

  6669: more executor threads,runnable, canceling threads, cleanup

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Changes:
  - all: https://git.openjdk.java.net/jmc/pull/135/files
  - new: https://git.openjdk.java.net/jmc/pull/135/files/be5fc13d..9b435a23

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=135&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=135&range=01-02

  Stats: 38 lines in 1 file changed: 9 ins; 8 del; 21 mod
  Patch: https://git.openjdk.java.net/jmc/pull/135.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/135/head:pull/135

PR: https://git.openjdk.java.net/jmc/pull/135