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_tb.v

@@ -0,0 +1,34 @@
+module top;
+    reg [56-1:0] in;
+    reg [2:0] select;
+
+    wire a;
+    wire [3:0] b;
+    wire [1:0] c;
+
+    Unpacker unpacker(in, select, a, b, c);
+
+    initial begin
+        $monitor("%d: %01b %04b %02b", select, a, b, c);
+        in = 'b01111011011011101111100111110111001010001011100110101000;
+        select = 0; #1;
+        select = 1; #1;
+        select = 2; #1;
+        select = 3; #1;
+        select = 4; #1;
+        select = 5; #1;
+        select = 6; #1;
+        select = 7; #1;
+        $finish;
+    end
+
+    // 0 1010 00
+    // 1 1100 11
+    // 0 1000 10
+    // 0 1110 01
+    // 0 0111 11
+    // 1 0111 11
+    // 1 0110 11
+    // 0 1111 01
+
+endmodule