### 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(String::num(3.141593, 3) == "3.142");
	CHECK(String::num_scientific(30000000) == "3e+07");
	CHECK(String::num_int64(3141593) == "3141593");
	CHECK(String::num_int64(0xA141593, 16) == "a141593");
	CHECK(String::num_int64(0xA141593, 16, true) == "A141593");
	CHECK(String::num(42.100023, 4) == "42.1"); 
	
	CHECK(String::num_real(1.0) == "1.0");
	CHECK(String::num_real(1.0, false) == "1");
	CHECK(String::num_real(9.9) == "9.9");
	CHECK(String::num_real(9.99) == "9.99");
	CHECK(String::num_real(9.999) == "9.999");
	CHECK(String::num_real(9.9999) == "9.9999");
	CHECK(String::num_real(3.141593) == "3.141593");
	CHECK(String::num_real(3.141) == "3.141"); 
#ifdef REAL_T_IS_DOUBLE
	CHECK_MESSAGE(String::num_real(123.456789) == "123.456789", "Prints the appropriate amount of digits for real_t = double.");
	CHECK_MESSAGE(String::num_real(-123.456789) == "-123.456789", "Prints the appropriate amount of digits for real_t = double.");
	CHECK_MESSAGE(String::num_real(Math_PI) == "3.14159265358979", "Prints the appropriate amount of digits for real_t = double.");
	CHECK_MESSAGE(String::num_real(3.1415f) == "3.1414999961853", "Prints more digits of 32-bit float when real_t = double (ones that would be reliable for double) and no trailing zero.");
#else
	CHECK_MESSAGE(String::num_real(123.456789) == "123.4568", "Prints the appropriate amount of digits for real_t = float.");
	CHECK_MESSAGE(String::num_real(-123.456789) == "-123.4568", "Prints the appropriate amount of digits for real_t = float.");
	CHECK_MESSAGE(String::num_real(Math_PI) == "3.141593", "Prints the appropriate amount of digits for real_t = float.");
	CHECK_MESSAGE(String::num_real(3.1415f) == "3.1415", "Prints only reliable digits of 32-bit float when real_t = float.");
#endif 
	
	CHECK(String::num(0.0000012345432123454321, -1) == "0.00000123454321"); 
	CHECK(String::num(0.0000012345432123454321) == "0.00000123454321"); 
	CHECK(String::num(-0.0000012345432123454321) == "-0.00000123454321");