ENH: Rework the CP2K basis set parser

[BvB93]

This PR rewrites the CP2K basis set parser, introducing the following two enhancements:

• Basis set aliases are now actually parsed and returned as distinct AtomBasisKey instances. In such case, a reference to parent is included via the new AtomBasisKey.alias field.
• The relevant readCp2KBasis function is now roughly an order of magnitude faster.

[codecov]

Codecov Report

Merging #282 (7c38430) into master (5a8c947) will decrease coverage by 0.06%.
The diff coverage is 95.55%.

@@            Coverage Diff             @@
##           master     #282      +/-   ##
==========================================
- Coverage   81.93%   81.87%   -0.07%     
==========================================
  Files          41       42       +1     
  Lines        2170     2190      +20     
  Branches      368      369       +1     
==========================================
+ Hits         1778     1793      +15     
- Misses        301      306       +5     
  Partials       91       91              

Impacted Files	Coverage Δ
src/qmflows/parsers/_cp2k_basis_parser.py	94.87% <94.87%> (ø)
src/qmflows/common.py	94.87% <100.00%> (+0.13%)	⬆️
src/qmflows/parsers/cp2KParser.py	73.37% <100.00%> (-2.54%)	⬇️

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