Validate Conv bias size (#32160)
This pull request strengthens input validation for the Conv operator by
adding explicit checks for the bias tensor shape and size, and adds a
new unit test to verify this behavior. The main changes are as follows:
**Input validation improvements:**
* Added a check in `Conv<T>::Compute` (and the float specialization) to
ensure that the bias tensor `B`, if provided, is a 1D tensor whose size
matches the number of output channels (`M`). If not, an informative
error message is returned.
[[1]](diffhunk://#diff-17bd0d956bdc88650a3b0fc11efe67ee921f0e2f0d5e5ab3e73925cd4bb510d7R75-R77)
[[2]](diffhunk://#diff-17bd0d956bdc88650a3b0fc11efe67ee921f0e2f0d5e5ab3e73925cd4bb510d7R261-R263)
**Testing enhancements:**
* Introduced a new test case `Conv2D_InvalidBiasSize` in
`conv_op_test.cc` to verify that the Conv operator correctly fails when
the bias tensor does not have the expected size, ensuring the new
validation logic works as intended.
