This adds patterns and a pass to convert the Arith dialect to EmitC. For
now, this covers arithemtic binary ops operating on floating point
types.
It is not checked within the patterns whether the types, such as the
Tensor type, are supported in the respective EmitC operations. If
unsupported types should be converted, the conversion will fail anyway
because no legal EmitC operation can be created. This can clearly be
improved in a follow up, also resulting in better error messages.
Functions for such checks should not solely be used in the conversions
and should also be (re)used in the verifier.
