tests: link atomic to all tests

[igchor]

Not only self_relative_ptr tests use atomics. On some platforms
(e.g. riscv64) -latomic is needed for a few other tests
(pool_cleanup, volatile_state).

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This change is 

[lukaszstolarczuk]

Reviewed 2 of 2 files at r1, 2 of 2 files at r2.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @igchor)

a discussion (no related file):
update readme with new tests' dependency...?

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[codecov]

Codecov Report

Merging #1132 (ea65a8e) into stable-1.11 (c68618e) will increase coverage by 0.11%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           stable-1.11    #1132      +/-   ##
===============================================
+ Coverage        95.86%   95.97%   +0.11%     
===============================================
  Files               48       48              
  Lines             6090     6090              
===============================================
+ Hits              5838     5845       +7     
+ Misses             252      245       -7     

Flag	Coverage Δ
tests_clang_debug_cpp17	95.81% <ø> (+0.03%)	⬆️
tests_gcc_debug	92.54% <ø> (+0.17%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ibpmemobj++/detail/self_relative_ptr_base_impl.hpp	97.10% <0.00%> (-0.05%)	⬇️
include/libpmemobj++/experimental/radix_tree.hpp	99.32% <0.00%> (+<0.01%)	⬆️
...ude/libpmemobj++/container/concurrent_hash_map.hpp	94.17% <0.00%> (+0.70%)	⬆️

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[lukaszstolarczuk]

Reviewed 1 of 1 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @igchor)

[karczex]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @igchor)