Try running pmemcheck tests with "--mult-stores=yes"

[igchor]

This should provide better test coverage for rapidcheck tests where we reopen the pmemstream multiple times.
This should mostly likely be run on internal infrastructure as part of stress tests (due to longer length).

[lukaszstolarczuk]

We may also set up some job(s) with tests using different pmem2 granularities - pmemcheck may catch some issues while e.g. entry appends fit (or not) within cachline/page size.