Initial fixes for Python 3.14

[cdce8p]

Tested against 3.14.0b1 locally. We might still need to adjust some things as more pre-release versions come out but this provides a good starting point in combination with #2731.

Relevant changes for Python 3.14

• typing.ByteString and collections.abc.ByteString were removed
  https://docs.python.org/3.13/library/typing.html#typing.ByteString
• The inference for pathlib parents changed back to pathlib._PathParents
• typing.Union was implemented in C and types.UnionType is now an alias for typing.Union
  gh-105499: Merge typing.Union and types.UnionType python/cpython#105511
  In theory we could think about renaming the UnionType class or at least think about if we want to change the pytype attribute
  

  astroid/astroid/bases.py

  Lines 738 to 742 in 5937f3d

  	class UnionType(BaseInstance):
  	"""Special node representing new style typing unions.
  	Proxied class is set once for all in raw_building.
  	"""

  
  

  astroid/astroid/bases.py

  Lines 761 to 762 in 5937f3d

  	def pytype(self) -> Literal["types.UnionType"]:
  	return "types.UnionType"

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.23%. Comparing base (3636bc2) to head (d52f79d).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
astroid/brain/brain_typing.py	80.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (88.88%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2747      +/-   ##
==========================================
+ Coverage   93.21%   93.23%   +0.02%     
==========================================
  Files          93       93              
  Lines       11072    11078       +6     
==========================================
+ Hits        10321    10329       +8     
+ Misses        751      749       -2     

Flag	Coverage Δ
linux	93.10% <88.88%> (+0.02%)	⬆️
pypy	93.23% <88.88%> (+0.02%)	⬆️
windows	93.22% <88.88%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
astroid/brain/brain_pathlib.py	92.00% <100.00%> (ø)
astroid/const.py	100.00% <100.00%> (ø)
astroid/brain/brain_typing.py	87.11% <80.00%> (-0.39%)	⬇️

... and 5 files with indirect coverage changes

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