### 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.
APPEND_CHAR(uint32_t(0x80 | (c & 0x3f))); // 
		} else if (c <= 0x001fffff) { // 
			APPEND_CHAR(uint32_t(0xf0 | ((c >> 18) & 0x07))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 12) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 6) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | (c & 0x3f))); // 
		} else if (c <= 0x03ffffff) { // 
			APPEND_CHAR(uint32_t(0xf8 | ((c >> 24) & 0x03))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 18) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 12) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 6) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | (c & 0x3f))); // 
		} else if (c <= 0x7fffffff) { // 
			APPEND_CHAR(uint32_t(0xfc | ((c >> 30) & 0x01))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 24) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 18) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 12) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((c >> 6) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | (c & 0x3f))); // 
		} else {
			// 
			print_unicode_error(vformat("Non scalar value (%x)", c), true);
			APPEND_CHAR(uint32_t(0xe0 | ((_replacement_char >> 12) & 0x0f))); // 
			APPEND_CHAR(uint32_t(0x80 | ((_replacement_char >> 6) & 0x3f))); // 
			APPEND_CHAR(uint32_t(0x80 | (_replacement_char & 0x3f))); // 
		}
	}
#undef APPEND_CHAR
	*cdst = 0; //
	return utf8s;