Allow string keys in `.eval`

[ricardoV94]

Description

eval is very useful for debugging, including interactive debugging during development. One issue is that required inputs must be passed by reference which is not always easy to do inside a given stack.

I usually have to play with ancestors to get a hold of the input variable. Instead it would be neat if we can get it by name if a string is used as a key in eval

import pytensor.tensor as pt

def create_expr():
  x = pt.scalar("x")
  y = pt.exp(x)
  return y

y = create_expr()
# Feature request:
y.eval({"x": 0})  # 1.0

If there are multiple variables with the same key name we could use the closest + warning or raise.

There is already a handy utility to find variables by name: https://pytensor.readthedocs.io/en/latest/library/graph/graph.html#pytensor.graph.basic.get_var_by_name

[Raj-Parekh24]

Hello @ricardoV94 ,

I am new to this project and want to make a contribution.

I am working on this issue. I have implemented a function that converts the dictionary with string keys to pytensor. The pytensor variable for the corresponding name is found using the function "get_var_by_name".

I am raising the PR please review it.