### 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.
static const uint8_t u8str[] = { 0x54, 0xC4, 0x93, 0xC5, 0xA1, 0x74, 0x00 };
	String x2 = String::utf8((const char *)u8str);
	String x3 = U"Tēšt";
	CHECK(x1.uri_decode() == x2);
	CHECK(x1.uri_decode() == x3);
	CHECK((x1 + x3).uri_decode() == (x2 + x3)); // Mixed unicode and URL encoded string, e.g. GTK+ bookmark.
	CHECK(x2.uri_encode() == x1);
	CHECK(x3.uri_encode() == x1);
	CHECK(s.uri_encode() == t);
	CHECK(t.uri_decode() == s);
}
TEST_CASE("[String] xml_escape/unescape") {
	String s = "\"Test\" <test@test&'test'>";
	CHECK(s.xml_escape(true).xml_unescape() == s);
	CHECK(s.xml_escape(false).xml_unescape() == s);
}
TEST_CASE("[String] xml_unescape") {
	// Named entities
	String input = "&quot;&amp;&apos;&lt;&gt;";
	CHECK(input.xml_unescape() == "\"&\'<>");
	// Numeric entities
	input = "&#x41;&#66;";
	CHECK(input.xml_unescape() == "AB");
	input = "&#0;&x#0;More text";
	Strxml_unescape();
	// Didn't put in a leading NUL and terminate the string
	CHECK(input.length() > 0);
	CHECK(input[0] != '\0');
	// Entity should be left as-is if invalid
	CHECK(input.xml_unescape() == input);