tests: test process switching using preload tests

[marcinslusarz]

Not all of them are used:

• "nested_dirs" is too slow with nvml 1.3
• "pool_locking" is extremely slow, even with nvml master
• "config_*" tests test only the initialization of libpmemfile

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This change is 

[krzycz]

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Reviewed 1 of 1 files at r1. Review status: all files reviewed at latest revision, all discussions resolved, some commit checks failed.

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Comments from Reviewable

[codecov[bot]]

Codecov Report

Merging #336 into master will increase coverage by 0.59%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #336      +/-   ##
==========================================
+ Coverage   77.11%   77.71%   +0.59%     
==========================================
  Files          92       92              
  Lines       14106    14108       +2     
  Branches     2021     2021              
==========================================
+ Hits        10878    10964      +86     
+ Misses       2457     2374      -83     
+ Partials      771      770       -1

Impacted Files	Coverage Δ
src/libpmemfile-posix/utils.c	71.87% <0%> (-1.57%)	:arrow_down:
src/libpmemfile-posix/read.c	92.51% <0%> (-0.69%)	:arrow_down:
src/libpmemfile-posix/rename.c	90.4% <0%> (-0.4%)	:arrow_down:
src/libpmemfile-posix/file.c	69.23% <0%> (-0.28%)	:arrow_down:
src/libpmemfile/path_resolve.c	88.81% <0%> (+0.14%)	:arrow_up:
src/libpmemfile-posix/data.c	89.61% <0%> (+0.38%)	:arrow_up:
src/libpmemfile/preload.c	47.02% <0%> (+1.39%)	:arrow_up:
src/libpmemfile-posix/hash_map.c	86.27% <0%> (+2.94%)	:arrow_up:
src/libpmemfile-posix/inode_array.c	78.75% <0%> (+5%)	:arrow_up:
src/libpmemfile-posix/inode.c	88.5% <0%> (+11.14%)	:arrow_up:
... and 1 more

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[sarahjelinek]

Reviewed 5 of 5 files at r2. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[sarahjelinek]

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Review status: :shipit: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

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Comments from Reviewable