### 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.
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 UTF16 (non-standard)") {
	ERR_PRINT_OFF
	static const char16_t u16str[] = { 0x0045, 0x304A, 0x3088, 0x3046, 0xDFA4, 0 };
	
	static const char32_t u32str[] = { 0x0045, 0x304A, 0x3088, 0x3046, 0xDFA4, 0 };
	String s;
	Error err = s.parse_utf16(u16str);
	CHECK(err == ERR_PARSE_ERROR);
	CHECK(s == u32str);
	Char16String cs = u16str;
	CHECK(String::utf16(cs) == s);
	ERR_PRINT_ON
}
TEST_CASE("[String] ASCII") {
	String s = U"Primero Leche";
	String t = s.ascii(false).get_data();
	CHECK(s == t);
	t = s.ascii(true).get_data();
	CHECK(s == t);
}
TEST_CASE("[String] Comparisons (equal)") {
	String s = "Test Compare";
	CHECK(s == "Test Compare");
	CHECK(s == U"Test Compare");