RFR: 8267893: Improve jtreg test failure handler do get native/mixed stack traces for cores and live processes [v2]

[Leonid Mesnik]

> EFH is improved to process cores and get mixed stack traces with jhsdb and native stack traces with gdb/lldb. It might be useful because hs_err doesn't contain info about all threads, sometimes it is even not generated.

Leonid Mesnik has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch 'efh' of https://github.com/lmesnik/jdk into efh
 - updated after comments from Igor

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4234/files
  - new: https://git.openjdk.java.net/jdk/pull/4234/files/68fd69d9..cb1eb944

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4234&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4234&range=00-01

  Stats: 47 lines in 7 files changed: 9 ins; 31 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4234.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4234/head:pull/4234

PR: https://git.openjdk.java.net/jdk/pull/4234