### 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.
String s(U"Wool");
	CHECK(u32scmp(s.get_data(), U"Wool") == 0);
}
TEST_CASE("[String] UTF8") {
	
	static const char32_t u32str[] = { 0x0045, 0x0020, 0x304A, 0x360F, 0x3088, 0x3046, 0x1F3A4, 0 };
	static const uint8_t u8str[] = { 0x45, 0x20, 0xE3, 0x81, 0x8A, 0xE3, 0x98, 0x8F, 0xE3, 0x82, 0x88, 0xE3, 0x81, 0x86, 0xF0, 0x9F, 0x8E, 0xA4, 0 };
	String s = u32str;
	Error err = s.parse_utf8(s.utf8().get_data());
	CHECK(err == OK);
	CHECK(s == u32str);
	err = s.parse_utf8((const char *)u8str);
	CHECK(err == OK);
	CHECK(s == u32str);
	CharString cs = (const char *)u8str;
	CHECK(String::utf8(cs) == s);
}
TEST_CASE("[String] UTF16") {
	
	static const char32_t u32str[] = { 0x0045, 0x0020, 0x304A, 0x360F, 0x3088, 0x3046, 0x1F3A4, 0 };
	static const char16_t u16str[] = { 0x0045, 0x0020, 0x304A, 0x360F, 0x3088, 0x3046, 0xD83C, 0xDFA4, 0 };
	String s = u32str;
	Error err = s.parse_utf16(s.utf16().get_data());
	CHECK(err == OK);
	CHECK(s == u32str);
	err = s.parse_utf16(u16str);
	CHECK(err == OK);
	CHECK(s == u32str);
	Char16String cs = u16str;
	CHECK(String::utf16(cs) == s);