[ImportVerilog]Support the delay control.

[hailongSun2000]

No description provided.

[hailongSun2000]

It's just a simple attempt. And I have a question about the timeUnit. Slang has calculated the truth time, but we cannot distinguish which is the correct timeUnit from s, ms, us, etc. For example:
(Is there a way to get the time unit 🤔 ?)

`timescale 10 ns/1 ns
assign #1.49 a = 1'b1;
assign #1.50 a = 1'b0;

assign #1us a = 1'b0;

AST:

delay": {
              "kind": "Delay",
              "expr": {
                "kind": "RealLiteral",
                "type": "realtime",
                "value": 0.1,
                "constant": "0.1"
              }

-----------------------------------------------
"delay": {
              "kind": "Delay",
              "expr": {
                "kind": "RealLiteral",
                "type": "realtime",
                "value": 0.2,
                "constant": "0.2"
              }

----------------------------------------------
"delay": {
              "kind": "Delay",
              "expr": {
                "kind": "TimeLiteral",
                "type": "realtime",
                "value": 100,
                "constant": "100"
              }

[likeamahoney]

`timescale 10 ns/1 ns
assign #1.49 a = 1'b1;
assign #1.50 a = 1'b0;

assign #1us a = 1'b0;

Hi! timeUnit from timescale directive is module defined property according to LRM (which should be specified outside the module definition). It can be founded at module definition slang json ast section :

  "definitions": [
    {
      "name": "m",
      "kind": "Definition",
      "addr": 5723682596352,
      "defaultNetType": "5723682914720 wire",
      "definitionKind": "Module",
      "defaultLifetime": "Static",
      "unconnectedDrive": "None",
      "timeScale": "10ns / 1ns"
    },
    {
      "name": "n",
      "kind": "Definition",
      "addr": 5723682587136,
      "defaultNetType": "5723682914720 wire",
      "definitionKind": "Module",
      "defaultLifetime": "Static",
      "unconnectedDrive": "None",
      "timeScale": "100ns / 1ns"
    }
  ]

from sv like this:

`timescale 10 ns/1 ns
module m();
endmodule

`timescale 100 ns/1 ns
module n();
endmodule