RFR: 7903415: jcstress: Accept non-sequential CPU ID topologies

[Aleksey Shipilev]

On some guest VMs / containers, sysfs only shows the subset of CPUs allocated for it. Current sysfs code and affinity handling code relies on CPU IDs to be consecutive. On those machines, sysfs parser fails and we fall back to naive topology. We can make it significantly better.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/127/files
 Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=127&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903415
  Stats: 1145 lines in 14 files changed: 972 ins; 25 del; 148 mod
  Patch: https://git.openjdk.org/jcstress/pull/127.diff
  Fetch: git fetch https://git.openjdk.org/jcstress pull/127/head:pull/127

PR: https://git.openjdk.org/jcstress/pull/127