Use numpy C-API einsum for unoptimized Einsum

[ricardoV94]

Description

When Einsum can't be optimized (because we don't know the static shapes) it stays as an OpFromGraph. We could replace it by a COp (as a cxx_only rewrite) in this case, that calls the numpy C function:

https://numpy.org/devdocs/reference/c-api/array.html#c.PyArray_EinsteinSum

pytensor/pytensor/tensor/rewriting/einsum.py

Lines 39 to 53 in f25a624

	@register_specialize
	@node_rewriter([Einsum])
	def inline_optimized_einsum(
	fgraph: FunctionGraph, node: Apply
	) -> list[TensorVariable] | None:
	"""Inline einsums that are already optimized.
	This allows the inner garph to be optimized with the rest of the graph, now that we got ordering right.
	"""
	op: Einsum = node.op
	if not op.optimized:
	return None
	return cast(list[TensorVariable], inline_ofg_node(node))