fix(python): Consistent behaviour when "infer_schema_length=0" for read_excel

[alexander-beedie]

Closes #16408.

• Ensures consistent behaviour between all supported engines when infer_schema_length == 0.; we expect no inference in this case, meaning all columns should be loaded as strings.
• Validated for "xlsx2csv", "openpyxl", and "calamine".
• Also covers read_ods.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.38%. Comparing base (c81ef69) to head (0926d99).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16840   +/-   ##
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  Coverage   81.38%   81.38%           
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  Files        1425     1425           
  Lines      187606   187684   +78     
  Branches     2697     2698    +1     
=======================================
+ Hits       152677   152741   +64     
- Misses      34434    34448   +14     
  Partials      495      495           

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