### 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.
const char *ptrtmp_limit = &p_utf8[p_len];
		int skip = 0;
		uint8_t c_start = 0;
		while (ptrtmp != ptrtmp_limit && *ptrtmp) {
			uint8_t c = *ptrtmp >= 0 ? *ptrtmp : uint8_t(256 + *ptrtmp);
			if (skip == 0) {
				if (p_skip_cr && c == '\r') {
					ptrtmp++;
					continue;
				}
				/* 
				if ((c & 0x80) == 0) {
					skip = 0;
				} else if ((c & 0xe0) == 0xc0) {
					skip = 1;
				} else if ((c & 0xf0) == 0xe0) {
					skip = 2;
				} else if ((c & 0xf8) == 0xf0) {
					skip = 3;
				} else if ((c & 0xfc) == 0xf8) {
					skip = 4;
				} else if ((c & 0xfe) == 0xfc) {
					skip = 5;
				} else {
					skip = 0;
					print_unicode_error(vformat("Invalid UTF-8 leading byte (%x)", c), true);
					decode_ = true;
				}
				c_start = c;
				if (skip == 1 && (c & 0x1e) == 0) {