### Godot version

v4.1.stable.official [970459615]

### System information

Windows 11

### Issue description

Using `String::pad_zeros` on a string containing digits with greater length than the argument `digits` raises the error `Parameter count should be a positive number.` of `String::repeat`, because it is called with a negative parameter.
(Actually this error is not 100% correct, it should be non-negative)

4.0 Code:
https://github.com/godotengine/godot/blob/c8e0bd50c57de91c061866db1de407f2e7a74acd/core/string/ustring.cpp#L4127-L4155

Example: `"2023".pad_zeros(2)`
`begin == 0`
`end == 4`
`end - begin < p_digits == false` => No "0" is inserted, the string is returned unchanged.

4.1 Code:
https://github.com/godotengine/godot/blob/ce5c6151fc498b39fe0c188045a4685e0f627854/core/string/ustring.cpp#L4266-L4290

Example: `"2023".pad_zeros(2)`
`begin == 0`
`end == 4`
`zeros_to_add == 2 - (4 - 0) == -2`
=> `s.insert(0, String("0").repeat(-2))` is called => Error.

I don't know why this was changed, but I think ensuring that `zeros_to_add > 0` should be ensured internally and not by the user. If this condition is not fullfilled the string should be returned unchanged as in the 4.0 implementation.

### Steps to reproduce

Try my above mentioned example in 4.0 and 4.1

### Minimal reproduction project

Not necessary.
*p_dst = '>';
				}
				eat = 4;
			} else if (p_src_len >= 4 && p_src[1] == 'l' && p_src[2] == 't' && p_src[3] == ';') {
				if (p_dst) {
					*p_dst = '<';
				}
				eat = 4;
			} else if (p_src_len >= 5 && p_src[1] == 'a' && p_src[2] == 'm' && p_src[3] == 'p' && p_src[4] == ';') {
				if (p_dst) {
					*p_dst = '&';
				}
				eat = 5;
			} else if (p_src_len >= 6 && p_src[1] == 'q' && p_src[2] == 'u' && p_src[3] == 'o' && p_src[4] == 't' && p_src[5] == ';') {
				if (p_dst) {
					*p_dst = '"';
				}
				eat = 6;
			} else if (p_src_len >= 6 && p_src[1] == 'a' && p_src[2] == 'p' && p_src[3] == 'o' && p_src[4] == 's' && p_src[5] == ';') {
				if (p_dst) {
					*p_dst = '\'';
				}
				eat = 6;
			} else {
				if (p_dst) {
					*p_dst = *p_src;
				}
				eat = 1;
			}
			if (p_dst) {