### 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 String base = U"Hello darkness\r\nMy old friend\nI've come to talk\rWith you again";
	String keep_cr;
	Error err = keep_cr.parse_utf8(base.utf8().get_data());
	CHECK(err == OK);
	CHECK(keep_cr == base);
	String no_cr;
	err = no_cr.parse_utf8(base.utf8().get_data(), -1, true); 
	CHECK(err == OK);
	CHECK(no_cr == base.replace("\r", ""));
}
TEST_CASE("[String] Invalid UTF8 (non-standard)") {
	ERR_PRINT_OFF
	static const uint8_t u8str[] = { 0x45, 0xE3, 0x81, 0x8A, 0xE3, 0x82, 0x88, 0xE3, 0x81, 0x86, 0xF0, 0x9F, 0x8E, 0xA4, 0xF0, 0x82, 0x82, 0xAC, 0xED, 0xA0, 0x81, 0 };
	
	static const char32_t u32str[] = { 0x45, 0x304A, 0x3088, 0x3046, 0x1F3A4, 0x20AC, 0xFFFD, 0 };
	String s;
	Error err = s.parse_utf8((const char *)u8str);
	CHECK(err == ERR_INVALID_DATA);
	CHECK(s == u32str);
	CharString cs = (const char *)u8str;
	CHECK(String::utf8(cs) == s);
	ERR_PRINT_ON
}
TEST_CASE("[String] Invalid UTF8 (unrecoverable)") {
	ERR_PRINT_OFF
	static const uint8_t u8str[] = { 0x45, 0xE3, 0x81, 0x8A, 0x8F, 0xE3, 0xE3, 0x98, 0x8F, 0xE3, 0x82, 0x88, 0xE3, 0x81, 0x86, 0xC0, 0x80, 0xF0, 0x9F, 0x8E, 0xA4, 0xF0, 0x82, 0x82, 0xAC, 0xED, 0xA0, 0x81, 0 };
	
	static const char32_t u32str[] = { 0x45, 0x304A, 0xFFFD, 0xFFFD, 0xFFFD, 0xFFFD, 0x3088, 0x3046, 0xFFFD, 0x1F3A4, 0x20AC, 0xFFFD, 0 };
	String s;
	Error err = s.parse_utf8((const char *)u8str);