DaphneDSL: Type casting matrices

[RetoKrummenacher]

The type conversion on matrices is not working.

A = rand(5,5,0.0,1.0,1,-1);
print(A);
B = as.matrix.f32(A);
# Output:
# JIT session error: Symbols not found: 
#[ _cast__DenseMatrix_float__DenseMatrix_double ]

[aristotelis96]

Thank you @RetoKrummenacher for this issue. PR #337 implemented the kernel for casts between different value types of a DenseMatrix, however src/runtime/local/kernels/kernels.json is missing the entries. I've created a PR that should fix this.