Validate MatMulFpQ4 shape inputs (#32032)
This pull request strengthens shape inference and input validation for
the `MatMulFpQ4` operator and adds new unit tests to ensure invalid
input shapes are properly rejected. The main focus is on improving error
handling and making the code more robust against malformed inputs.
**Shape inference and validation improvements:**
* Added checks to ensure all relevant input tensors (`A`, `B`, and
`B_shape`) have shapes before proceeding with shape inference in
`matmulQ4ShapeInference` (`contrib_defs.cc`).
* Improved validation for the `B` input to require it to be a 1-D tensor
with a known, non-negative size, and for the `B_shape` input to require
it to be a 1-D int64 tensor of length 2 (`contrib_defs.cc`).
* Added a check to ensure the `B_shape` initializer contains exactly two
int64 values before using its data (`contrib_defs.cc`).
* Fixed the validation for the packed `B` tensor to correctly check its
size against the expected pack size, removing an incorrect logical
condition (`contrib_defs.cc`).
**Unit test additions:**
* Added new negative tests in `matmul_fpq4_test.cc` to verify that
invalid input shapes for `B` and `B_shape` are properly rejected,
including cases for scalar and short initializers.
