fix(python): Ensure write_excel recognises the Array dtype and writes it out as a string

[alexander-beedie]

The function was written before we had the Array dtype and the is_nested() method on the dtype class, so explicitly enumerated the dtypes that needed to be cast to string on sheet export - and therefore missed Array.

• Now takes advantage of .is_nested() to guarantee that we consistently identify dtypes that Excel doesn't work with natively (List, Array, Struct).

• Also made a few micro-optimisations, eg: df.height instead of len(df), and df.width instead of len(df.columns). Note that we can make this change in more places, avoiding the indirect/function call - I'll follow up with a separate PR for that.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.10%. Comparing base (c3d317e) to head (a9d2a5b).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20994      +/-   ##
==========================================
- Coverage   79.21%   79.10%   -0.12%     
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  Files        1583     1583              
  Lines      225082   225843     +761     
  Branches     2581     2600      +19     
==========================================
+ Hits       178299   178646     +347     
- Misses      46193    46606     +413     
- Partials      590      591       +1     

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[ritchie46]

Also made a few micro-optimisations, eg: df.height instead of len(df), and df.width instead of len(df.columns). Note that we can make this change in more places, avoiding the indirect/function call - I'll follow up with a separate PR for that.

Yeah, good one. Especially the df.columns, which is an allocation.