[BUG] `Trajectory` `_atom_cache` issues

[oerc0122]

Description of the error Atom cache could be implemented as a @functools.cached_property. However, it also creates duplicate cache entries for np.str_("C") and "C".

Describe the expected result No dups? Standard implementation.

Describe the actual result Custom implementation

Suggested fix Use functools.cached_property ensure types are cast before entry (possibly using functools.singledispatchmethod to cast)

Additional details N/A