TinyJit does not update bound values in symbolic shape

[chenyu]

repro

from tinygrad import Tensor, TinyJit, Variable

@TinyJit
def f(t): return t + 1

for i in range(1, 5):
  vi = Variable("i", 1, 10).bind(i)
  t = f(Tensor.rand(i).reshape(vi))
  print(f"{t.shape=}")

outputs

t.shape=(Variable('i', 1, 10).bind(1),)
t.shape=(Variable('i', 1, 10).bind(2),)
t.shape=(Variable('i', 1, 10).bind(2),)
t.shape=(Variable('i', 1, 10).bind(2),)

without TinyJit, it outputs

t.shape=(Variable('i', 1, 10).bind(1),)
t.shape=(Variable('i', 1, 10).bind(2),)
t.shape=(Variable('i', 1, 10).bind(3),)
t.shape=(Variable('i', 1, 10).bind(4),)

we can either update the shape after jit call, or enforce that Variable can only be registered inside the jitted function