Add assertions to SplatElementsAttr and ConstantOp builders and fix failures

1) Fix FloatAttr type inconsistency in conversion from tf.FusedBatchNorm to TFLite ops

We used to compose the splat tensor out of the scalar epsilon attribute by using the
type of the variance operand. However, the epsilon attribute may have a different
bitwidth than the one in the variance operand. So it ends up we were creating
inconsistent types within the FloatAttr itself.

2) Fix SplatElementsAttr type inconsistency in AnnotateInputArrays

We need to create the zero-valued attribute according to the type provided as the
command-line arguments.

3) Concretize the result type of tf.Shape constant folding test case

Currently the resultant constant is created by the constant folding harness, using
the result type of the original op as the constant's result type. That can be
a different type than the constant's internal DenseElementsAttr.

PiperOrigin-RevId: 230244665