Fix cyclic references in shared_ptr [15831]

[jparisu]

This PR fixes a cycle between shared ptrs that implies memory leaks.

Pending to:

• Add doxygen
• Check ASAN in all tests
• Check ASAN in dump/load
• Add specific fragil_ptr tests (Im afraid not gonna happen)

Merge after:

• Add flaky test labels and update CI so flakys are run in another job #175
• Fix singleton in StatisticsBackendData [15841] #172

[MiguelCompany]

@jparisu Please rebase and fix conflicts here

[MiguelCompany]

Partial review: fragile_ptr template

[MiguelCompany]

@jparisu Please rebase

[codecov]

Codecov Report

Base: 58.08% // Head: 58.15% // Increases project coverage by +0.06% 🎉

Coverage data is based on head (85425b4) compared to base (04e66d5).
Patch coverage: 96.49% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #174      +/-   ##
==========================================
+ Coverage   58.08%   58.15%   +0.06%     
==========================================
  Files          32       33       +1     
  Lines        4345     4364      +19     
  Branches     2318     2322       +4     
==========================================
+ Hits         2524     2538      +14     
+ Misses         59       57       -2     
- Partials     1762     1769       +7     

Impacted Files	Coverage Δ
...fastdds_statistics_backend/exception/Exception.hpp	50.00% <ø> (ø)
src/cpp/database/entities.hpp	100.00% <ø> (ø)
src/cpp/exception/Exception.cpp	87.50% <ø> (-1.98%)	⬇️
src/cpp/database/database.hpp	64.70% <75.00%> (-0.36%)	⬇️
src/cpp/types/fragile_ptr.hpp	97.87% <97.87%> (ø)
src/cpp/StatisticsBackendData.cpp	62.42% <100.00%> (ø)
src/cpp/database/entities.cpp	95.74% <100.00%> (ø)
src/cpp/database/database.cpp	51.30% <0.00%> (-0.29%)	⬇️

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[MiguelCompany]

LGTM. Just uncrustify and we're done

[MiguelCompany]

LGTM