chore: deprecate read/writeStr, placeInLattice method

[stevenhua0320]

@sbillinge ready to review. Note that in Structure class we have a private camcelcase method that we need to deprecate, but I assume we don't have user call this function, so I only change the camelcase to lowercase and its corresponding usage.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (793f5b0) to head (e66ddbe).
⚠️ Report is 3 commits behind head on v3.4.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           v3.4.0     #161      +/-   ##
==========================================
+ Coverage   98.95%   98.97%   +0.01%     
==========================================
  Files          13       13              
  Lines        1919     1951      +32     
==========================================
+ Hits         1899     1931      +32     
  Misses         20       20              

Files with missing lines	Coverage Δ
tests/test_p_cif.py	99.63% <100.00%> (+0.03%)	⬆️
tests/test_p_discus.py	98.85% <100.00%> (ø)
tests/test_p_pdffit.py	99.41% <100.00%> (ø)
tests/test_parsers.py	99.47% <100.00%> (ø)
tests/test_structure.py	99.80% <100.00%> (+<0.01%)	⬆️

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