Eliminate Need to call Loaders.LoadElements

[nbollis]

Every time you needed to use chemical formulas in mzLib you would need to first call Loaders.LoadElements(). This was eliminated by moving the loading from UsefulProteomicDatabases.PeriodicTableLoader to the static constructor of PeriodicTable.

Removed redundant calls to Loaders.LoadElements() across multiple test and production files in the mzLib project while ensuring culture still gets set in the testing project.

[codecov]

Codecov Report

Attention: Patch coverage is 97.10145% with 2 lines in your changes missing coverage. Please review.

Project coverage is 77.75%. Comparing base (7cdd05d) to head (1ddfceb).

Files with missing lines	Patch %	Lines
mzLib/Chemistry/PeriodicTable.cs	97.10%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #833      +/-   ##
==========================================
- Coverage   77.76%   77.75%   -0.02%     
==========================================
  Files         230      229       -1     
  Lines       34171    34159      -12     
  Branches     3541     3540       -1     
==========================================
- Hits        26574    26560      -14     
- Misses       6991     6993       +2     
  Partials      606      606              

Files with missing lines	Coverage Δ
mzLib/FlashLFQ/FlashLfqEngine.cs	92.40% <ø> (-0.01%)	⬇️
mzLib/Readers/Bruker/BrukerFileReader.cs	79.25% <ø> (-0.07%)	⬇️
mzLib/Readers/Mgf/Mgf.cs	92.14% <ø> (-0.09%)	⬇️
mzLib/Readers/MzML/Mzml.cs	90.68% <ø> (-0.03%)	⬇️
mzLib/Readers/Thermo/ThermoRawFileReader.cs	81.21% <ø> (-0.11%)	⬇️
mzLib/UsefulProteomicsDatabases/Loaders.cs	97.32% <ø> (-1.11%)	⬇️
mzLib/Chemistry/PeriodicTable.cs	98.07% <97.10%> (-1.93%)	⬇️