verilog: fix sizing of constant args for tasks/functions

- Simplify synthetic localparams for normal calls to update their width
    - This step was inadvertently removed alongside `added_mod_children`
- Support redeclaration of constant function arguments
    - `eval_const_function` never correctly handled this, but the issue
      was not exposed in the existing tests until the recent change to
      always attempt constant function evaluation when all-const args
      are used
- Check asserts in const_arg_loop and const_func tests
- Add coverage for width mismatch error cases

tests/various/const_func.sv

@@ -0,0 +1,86 @@
+module Example(outA, outB, outC, outD);
+    parameter OUTPUT = "FOO";
+    output wire [23:0] outA;
+    output wire [23:0] outB;
+    output reg outC, outD;
+    function automatic [23:0] flip;
+        input [23:0] inp;
+        flip = ~inp;
+    endfunction
+
+    generate
+        if (flip(OUTPUT) == flip("BAR"))
+            assign outA = OUTPUT;
+        else
+            assign outA = 0;
+
+        case (flip(OUTPUT))
+            flip("FOO"): assign outB = OUTPUT;
+            flip("BAR"): assign outB = 0;
+            flip("BAZ"): assign outB = "HI";
+        endcase
+
+        genvar i;
+        initial outC = 0;
+        for (i = 0; i != flip(flip(OUTPUT[15:8])); i = i + 1)
+            if (i + 1 == flip(flip("O")))
+                initial outC = 1;
+    endgenerate
+
+    integer j;
+    initial begin
+        outD = 1;
+        for (j = 0; j != flip(flip(OUTPUT[15:8])); j = j + 1)
+            if (j + 1 == flip(flip("O")))
+                outD = 0;
+    end
+endmodule
+
+module top(out);
+    wire [23:0] a1, a2, a3, a4;
+    wire [23:0] b1, b2, b3, b4;
+    wire        c1, c2, c3, c4;
+    wire        d1, d2, d3, d4;
+    Example          e1(a1, b1, c1, d1);
+    Example #("FOO") e2(a2, b2, c2, d2);
+    Example #("BAR") e3(a3, b3, c3, d3);
+    Example #("BAZ") e4(a4, b4, c4, d4);
+
+    output wire [24 * 8 - 1 + 4 :0] out;
+    assign out = {
+        a1, a2, a3, a4,
+        b1, b2, b3, b4,
+        c1, c2, c3, c4,
+        d1, d2, d3, d4};
+
+    function signed [31:0] negate;
+        input integer inp;
+        negate = ~inp;
+    endfunction
+    parameter W = 10;
+    parameter X = 3;
+    localparam signed Y = $floor(W / X);
+    localparam signed Z = negate($floor(W / X));
+
+    always_comb begin
+        assert(a1 == 0);
+        assert(a2 == 0);
+        assert(a3 == "BAR");
+        assert(a4 == 0);
+        assert(b1 == "FOO");
+        assert(b2 == "FOO");
+        assert(b3 == 0);
+        assert(b4 == "HI");
+        assert(c1 == 1);
+        assert(c2 == 1);
+        assert(c3 == 0);
+        assert(c4 == 0);
+        assert(d1 == 0);
+        assert(d2 == 0);
+        assert(d3 == 1);
+        assert(d4 == 1);
+
+        assert(Y == 3);
+        assert(Z == ~3);
+    end
+endmodule