Remove all references to _infer

[DanielNoord]

Steps

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Description

Blocked by #2167.

This would be the next step towards the new way of doing inference. We no longer have any internal references to _infer() or assignments to it.
Since this is private API we don't need a news entry.

Next step would be to start transitioning some of the calls to infer() to be infer_object.

Type of Changes

	Type
✓	🔨 Refactoring

Related Issue

[codecov]

Codecov Report

Merging #2168 (c8c01ef) into main (0740a0d) will increase coverage by 0.01%.
The diff coverage is 98.95%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2168      +/-   ##
==========================================
+ Coverage   92.53%   92.55%   +0.01%     
==========================================
  Files          94       94              
  Lines       10804    10825      +21     
==========================================
+ Hits         9998    10019      +21     
  Misses        806      806              

Flag	Coverage Δ
linux	92.31% <98.95%> (+0.01%)	⬆️
pypy	87.51% <98.95%> (+0.02%)	⬆️
windows	92.14% <98.95%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
astroid/nodes/node_classes.py	94.86% <ø> (-0.02%)	⬇️
astroid/inference.py	94.96% <98.90%> (+0.38%)	⬆️
astroid/nodes/node_ng.py	91.86% <100.00%> (-0.82%)	⬇️
astroid/objects.py	94.26% <100.00%> (+0.40%)	⬆️

[jacobtylerwalls]

Superseded by #2171