additional param type conversion bug fixes

- general refactoring throughout
- improved metrics for dropping unneeded modules
- fix re-visiting a converted instance in the same pass

test/basic/paramtype_delay.sv

@@ -15,7 +15,8 @@ module mod #(
 endmodule
 
 module top;
-    typedef struct packed { byte y; } W;
+    parameter type BASE = byte;
+    typedef struct packed { BASE y; } W;
     W w;
     typedef struct packed { type(w) x, y; } V;
     V v;

test/basic/paramtype_expr.sv

+module mod #(
+    parameter type T = logic
+);
+    initial $display("$bits(T) = %0d", $bits(T));
+endmodule
+
+module top;
+    parameter SIZE = 8;
+    mod #(logic [SIZE-1:0]) m();
+endmodule

test/basic/paramtype_expr.v

+module mod #(
+    parameter S = 1
+);
+    initial $display("$bits(T) = %0d", S);
+endmodule
+
+module top;
+    parameter SIZE = 8;
+    mod #(SIZE) m();
+endmodule

test/basic/paramtype_recurse.sv

@@ -28,4 +28,4 @@ module top_2; bar #(byte, 3) x(); endmodule
 module top_3; foo #(bit, 4) x(); endmodule
 module top_4; bar #(bit, 5) x(); endmodule
 
-module top; endmodule
+module top; foo x(); endmodule

test/basic/paramtype_recurse.v

@@ -48,4 +48,4 @@ module top_2; bar_byte #(3) x(); endmodule
 module top_3; foo_bit #(4) x(); endmodule
 module top_4; bar_bit #(5) x(); endmodule
 
-module top; endmodule
+module top; foo_bit #(0) x(); endmodule