several major fixes surrounding packed arrays

- entirely new PackedArray conversion (always flattens)
- typedef and struct correctly order packed ranges when combining types
- Stmt LHS traversal no longer traverses nested statements to avoid double conversion
- Logic conversion applies to `initial` blocks`
- new and modified tests to cover these cases

test/basic/struct_array.v

@@ -0,0 +1,13 @@
+module Unpacker(in, select, a, b, c);
+    parameter WIDTH = 8;
+    input wire [WIDTH-1:0][6:0] in;
+    input wire [$clog2(WIDTH)-1:0] select;
+    output wire a;
+    output wire [3:0] b;
+    output wire [1:0] c;
+    wire [6:0] p;
+    assign p = in[select];
+    assign a = p[6:6];
+    assign b = p[5:2];
+    assign c = p[1:0];
+endmodule