### 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.
keys.push_back("man");
	String s = "Pretty Woman";
	int key = 0;
	CHECK(s.findmk(keys, 0, &key) == 3);
	CHECK(key == 1);
	CHECK(s.findmk(keys, 5, &key) == 9);
	CHECK(key == 2);
}
TEST_CASE("[String] Find and replace") {
	String s = "Happy Birthday, Anna!";
	s = s.replace("Birthday", "Halloween");
	CHECK(s == "Happy Halloween, Anna!");
	s = s.replace_first("H", "W");
	CHECK(s == "Wappy Halloween, Anna!");
}
TEST_CASE("[String] Insertion") {
	String s = "Who is Frederic?";
	s = s.insert(s.find("?"), " Chopin");
	CHECK(s == "Who is Frederic Chopin?");
}
TEST_CASE("[String] Erasing") {
	String s = "Josephine is such a cute girl!";
	s = s.erase(s.find("cute "), String("cute ").length());
	CHECK(s == "Josephine is such a girl!");
}
TEST_CASE("[String] Number to string") {
	CHECK(String::num(0) == "0");
	CHECK(String::num(0.0) == "0"); 
	CHECK(String::num(-0.0) == "-0"); 
	CHECK(String::num(3.141593) == "3.141593");