support for attributes in unary, binary, and ternary expressions

Co-authored-by: qcorradi <[email protected]>
Co-authored-by: Zachary Snow <[email protected]>

test/basic/expr_attr.sv

@@ -0,0 +1,4 @@
+module top;
+    wire a, b, c, d, e;
+    assign a = b ? (* ternary *) ~^ (* unary *) c : d & (* binary *) e;
+endmodule

test/basic/expr_attr.sv.pat

@@ -0,0 +1,3 @@
+affirm (* unary *)
+affirm (* binary *)
+affirm (* ternary *)