### 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.
char32_t *dst = ptrw();
	dst[str_size] = 0;
	int skip = 0;
	uint32_t unichar = 0;
	while (cstr_size) {
		uint8_t c = *p_utf8 >= 0 ? *p_utf8 : uint8_t(256 + *p_utf8);
		if (skip == 0) {
			if (p_skip_cr && c == '\r') {
				p_utf8++;
				continue;
			}
			/* 
			if ((c & 0x80) == 0) {
				*(dst++) = c;
				unichar = 0;
				skip = 0;
			} else if ((c & 0xe0) == 0xc0) {
				unichar = (0xff >> 3) & c;
				skip = 1;
			} else if ((c & 0xf0) == 0xe0) {
				unichar = (0xff >> 4) & c;
				skip = 2;
			} else if ((c & 0xf8) == 0xf0) {
				unichar = (0xff >> 5) & c;
				skip = 3;
			} else if ((c & 0xfc) == 0xf8) {
				unichar = (0xff >> 6) & c;
				skip = 4;
			} else if ((c & 0xfe) == 0xfc) {
				unichar = (0xff >> 7) & c;