### Godot version

4.0

### System information

All OS/Hardware

### Issue description

Not sure if it's a bug / inconsistency or a willingness 😄

When writing numbers in GDScript, we can use `_` character to make number more readable for a human. Rules for this character differ depending on where it is used : before or in decimal part, making its usage inconsistent. 
- When use before decimal part, only an underscore can not follow another undersocre
- In decimal part, multiple underscores can be write without any complaint of tokenizer



### Steps to reproduce

Here is test functions to illustrate

```gdscript
func test_number_allowed_without_error() -> void:
    var a:int = 1_2_3_4_5_6
    var b:int = 123_456
    var c:int = 1.2_3_4_5_6
    var d:int = 1.2_____3_____4____5_____6
    var e:int = 1._2_3_4_5
    var f:int = 1.________23456

func test_number_not_allowed() -> void:
    var a:int = 1__2
    var b:int = 1__2.1__2
    var c:int = _1.23456
```

With a screen to show editor syntax errors

![image](https://user-images.githubusercontent.com/121614863/220851058-38439a3f-3ba8-40fa-9556-a0faf045c943.png)

### Minimal reproduction project

N/A
return;
		}
		
		if (indent_char == '\0') {
			
			indent_char = current_indent_char;
		} else if (current_indent_char != indent_char) {
			Token error = make_error(vformat("Used %s character for indentation instead of %s as used before in the file.",
					_get_indent_char_name(current_indent_char), _get_indent_char_name(indent_char)));
			error.start_line = line;
			error.start_column = 1;
			error.leftmost_column = 1;
			error.rightmost_column = column;
			push_error(error);
		}
		
		
		int previous_indent = 0;
		if (indent_level() > 0) {
			previous_indent = indent_stack.back()->get();
		}
		if (indent_count == previous_indent) {
			
			return;
		}
		if (indent_count > previous_indent) {
			
			indent_stack.push_back(indent_count);
			pending_indents++;
		} else {