Magma should raise an error when an operator with an integer requires truncation

[leonardt]

Here's an example:

import magma as m


class Foo(m.Circuit):
    io = m.IO(x=m.In(m.Bits[2]), y=m.Out(m.Bits[2]))
    io.y @= io.x & 4


m.compile("build/Foo", Foo, inline=True)

This produces

module Foo (
    input [1:0] x,
    output [1:0] y
);
assign y = x & 2'h0;
endmodule

Rather than implicitly truncating the integer value, we should raise and error and force the user to acknowledge that the value will be truncated by doing the truncation themselves.