Remove `VarName` from codebase

[ricardoV94]

Description

Why are we defining a new string type? An alias is sufficient if we even need it, but I think str is just fine. Also all PyTensor variables have a name attribute we don't need to call getattr(variable, "name") it may just be None

pymc/pymc/util.py

Line 61 in f6bfdfd

VarName = NewType("VarName", str)

pymc/pymc/util.py

Lines 253 to 255 in f6bfdfd

	def get_var_name(var) -> VarName:
	"""Get an appropriate, plain variable name for a variable."""
	return VarName(str(getattr(var, "name", var)))