RFR: CODETOOLS-7902903: jcstress: Optimize sanity preset mode

[Aleksey Shipilev]

It looks like "sanity" mode ignores the min/max stride settings, and so we enter sanityCheck_Footprints for it, producing more samples than we need. This makes "sanity" unnecessarily slow.

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Commit messages:
 - 7902903: jcstress: Optimize sanity preset mode

Changes: https://git.openjdk.java.net/jcstress/pull/34/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=34&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902903
  Stats: 22 lines in 1 file changed: 9 ins; 8 del; 5 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/34.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/34/head:pull/34

PR: https://git.openjdk.java.net/jcstress/pull/34