Improve static shape inference in grappler by propagating tensors_as_shapes better:

Currently, static shape inference propagates shapes of tensors, but in some cases, we do need values; for this, we use input_tensors (from Const input tensor) and input_tensors_as_shapes and output_tensors_as_shapes (these are ShapeHandle format, but has values, currently only for 1D vector).

This CL enhances propagation of input_tensors_as_shapes and output_tensors_as_shapes to improve static shape inference.

(1) forward scalar Const as input_tensors_as_shapes (currently, only 1D vector),
(2) export input_tensors_as_shapes, output const tensor, and output_tensors_as_shapes to the values of inferred input/output TensorProperties (currently, only input const tensors are exported as values),
(3) use input_tensors_as_shapes as Const tensor to function input (currently, only Const tensors),
(4) forward input_tensors_as_shapes to output_tensors_as_shapes for Identity op,
(5) when Pack op concats scalar values to form output_tensors_as_shapes, currently it uses only input_tensors (from Const input tensors), but this CL change Pack to use input_tensors_as_shapes as well.

PiperOrigin-RevId: 212696959