[xlscc] ! Operator creates incorrect logic

Please see included example outlining ! Operator creates incorrect logic.
This is a regression from previous behavior.

Test case:
[test.cc.txt](https://github.com/google/xls/files/14620434/test.cc.txt)

Current result:
assign thisid6 = in1[0];
assign out = {30'h0000_0000, thisid6, 1'h0};
[xls_test.v.txt](https://github.com/google/xls/files/14620461/xls_test.v.txt)

expected results:
assign p0_thisid6_comb = {{32{in1[31]}}, in1};
assign out = {30'h0000_0000, p0_thisid6_comb != 64'h0000_0000_0000_0000, 1'h0};
[ref_test.v.txt](https://github.com/google/xls/files/14620433/ref_test.v.txt)

Runner:
[runme.sh.txt](https://github.com/google/xls/files/14620438/runme.sh.txt)

Thanks for taking a look!