CLN: remove compat.add_metaclass

[topper-123]

• xref CLN: remove PY2 #25725

This removes the compat.add_metaclass function from the code base and replaces it with a metaclass parameter in class instation.

I don't understand why ExcelWriter needs to use a abc.ABCMeta metaclass, as the class is being used directly in the code base and I thought abstract classes couldn't be instantiated, but needed subclassing. I've kept abc.ABCMeta metaclass in ExcelWriter, but would appreciate advice.

[codecov]

Codecov Report

Merging #26165 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #26165      +/-   ##
==========================================
- Coverage   91.98%   91.97%   -0.01%     
==========================================
  Files         175      175              
  Lines       52377    52365      -12     
==========================================
- Hits        48180    48165      -15     
- Misses       4197     4200       +3

Flag	Coverage Δ
#multiple	90.53% <100%> (-0.01%)	⬇️
#single	40.7% <100%> (-0.16%)	⬇️

Impacted Files	Coverage Δ
pandas/compat/__init__.py	92.85% <ø> (+0.7%)	⬆️
pandas/io/excel/_base.py	92.78% <100%> (-0.04%)	⬇️
pandas/tseries/holiday.py	93.1% <100%> (-0.07%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/frame.py	96.9% <0%> (-0.12%)	⬇️

---

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[codecov]

Codecov Report

Merging #26165 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #26165      +/-   ##
==========================================
- Coverage   91.98%   91.97%   -0.01%     
==========================================
  Files         175      175              
  Lines       52377    52365      -12     
==========================================
- Hits        48180    48165      -15     
- Misses       4197     4200       +3

Flag	Coverage Δ
#multiple	90.53% <100%> (-0.01%)	⬇️
#single	40.7% <100%> (-0.16%)	⬇️

Impacted Files	Coverage Δ
pandas/compat/__init__.py	92.85% <ø> (+0.7%)	⬆️
pandas/io/excel/_base.py	92.78% <100%> (-0.04%)	⬇️
pandas/tseries/holiday.py	93.1% <100%> (-0.07%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/frame.py	96.9% <0%> (-0.12%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dc86509...6932c6e. Read the comment docs.