Fix singleton in StatisticsBackendData [15841]

[jparisu]

Fix a Memory Leak problem related with Singleton StatisticsBackendData

This PR fixes some ASAN problems related with StatisticsBackendData, but not all memory errors. Thus the asan job is expected to keep failing.

Merge after:

• Add flaky test labels and update CI so flakys are run in another job #175

[codecov]

Codecov Report

Base: 57.82% // Head: 58.08% // Increases project coverage by +0.26% 🎉

Coverage data is based on head (cf468ca) compared to base (1e368df).
Patch coverage: 55.43% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #172      +/-   ##
==========================================
+ Coverage   57.82%   58.08%   +0.26%     
==========================================
  Files          31       32       +1     
  Lines        4320     4345      +25     
  Branches     2310     2318       +8     
==========================================
+ Hits         2498     2524      +26     
+ Misses         60       59       -1     
  Partials     1762     1762              

Impacted Files	Coverage Δ
src/cpp/database/database.hpp	65.06% <ø> (ø)
src/cpp/StatisticsBackendData.cpp	62.42% <45.45%> (-3.23%)	⬇️
src/cpp/StatisticsBackend.cpp	47.40% <48.88%> (+2.07%)	⬆️
src/cpp/database/database.cpp	51.59% <100.00%> (+0.11%)	⬆️
src/cpp/detail/ScopeExit.hpp	100.00% <100.00%> (ø)

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[MiguelCompany]

LGTM with correct CI