### 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.
}
	bool decode_error = false;
	{
		const char16_t *ptrtmp = p_utf16;
		const char16_t *ptrtmp_limit = &p_utf16[p_len];
		uint32_t c_prev = 0;
		bool skip = false;
		while (ptrtmp != ptrtmp_limit && *ptrtmp) {
			uint32_t c = (byteswap) ? BSWAP16(*ptrtmp) : *ptrtmp;
			if ((c & 0xfffffc00) == 0xd800) { // 
				if (skip) {
					print_unicode_error(vformat("Unpaired  (%x [trail?] %x)", c_prev, c));
					decode_error = true;
				}
				skip = true;
			} else if ((c & 0xfffffc00) == 0xdc00) { // 
				if (skip) {
					str_size--;
				} else {
					print_unicode_error(vformat("Unpaired  (%x [lead?] %x)", c_prev, c));
					decode_error = true;
				}
				skip = false;
			} else {
				skip = false;
			}
			c_prev = c;
			str_size++;
			cstr_size++;
			ptrtmp++;