### 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.
if (p_keys.size() == 0) {
		return -1;
	}
	//
	const  *keys = &p_keys[0];
	int key_count = p_keys.size();
	int len = length();
	if (len == 0) {
		return -1; // 
	}
	const char32_t *src = get_data();
	for (int i = p_from; i < len; i++) {
		bool found = true;
		for (int k = 0; k < key_count; k++) {
			found = true;
			if (r_key) {
				*r_key = k;
			}
			const char32_t *cmp = keys[k].get_data();
			int l = keys[k].length();
			for (int j = 0; j < l; j++) {
				int read_pos = i + j;
				if (read_pos >= len) {
					found = false;
					break;
				}
				if (src[read_pos] != cmp[j]) {
					found = false;
					break;
				}