### 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.
}
TEST_CASE("[String] Test chr") {
	CHECK(String::chr('H') == "H");
	CHECK(String::chr(0x3012)[0] == 0x3012);
	ERR_PRINT_OFF
	CHECK(String::chr(0xd812)[0] == 0xfffd); 
	CHECK(String::chr(0x20d812)[0] == 0xfffd); 
	ERR_PRINT_ON
}
TEST_CASE("[String] Operator []") {
	String a = "Kugar Sane";
	a[0] = 'S';
	a[6] = 'C';
	CHECK(a == "Sugar Cane");
	CHECK(a[1] == 'u');
	CHECK(a.unicode_at(1) == 'u');
}
TEST_CASE("[String] Case function test") {
	String a = "MoMoNgA";
	CHECK(a.to_upper() == "MOMONGA");
	CHECK(a.to_lower() == "momonga");
}
TEST_CASE("[String] Case compare function test") {
	String a = "MoMoNgA";
	CHECK(a.casecmp_to("momonga") != 0);
	CHECK(a.nocasecmp_to("momonga") == 0);
}
TEST_CASE("[String] Natural compare function test") {
	String a = "img2.png";
	CHECK(a.nocasecmp_to("img10.png") > 0);