Add more tests to scolapasta-hex

[lopopolo]

Also add impl<'a, const N: usize> From<&'a [u8; N]> for Hex impl.

I'll let ChatGPT describe the tests we added together.

Test Description

The test_try_encode function tests the try_encode function by encoding a byte slice and asserting that the result matches the expected output.

The test_try_encode_into function tests the try_encode_into function by encoding a byte slice into a pre-allocated String and asserting that the resulting String matches the expected output.

The test_format_into function tests the format_into function by encoding a byte slice into a pre-allocated String using the fmt::Write trait and asserting that the resulting String matches the expected output.

The test_write_into function (enabled only with the std feature) tests the write_into function by encoding a byte slice into a vector of bytes using the io::Write trait and asserting that the resulting vector of bytes matches the expected output.

The test_hex_iterator function tests the Hex iterator by creating an iterator from a string, collecting the elements into a String, and asserting that the resulting String matches the expected output.

Here's a brief overview of the additional tests:

1. literal_exhaustive: This test iterates over all possible byte values (0 to 255) and checks that the corresponding hex digits are correctly generated.

2. test_hex_iterator_with_remaining_escaped_byte: This test verifies that the Hex iterator handles a sequence of bytes correctly, even if there is a remaining escaped byte.

3. test_hex_iterator_empty_after_exhausted: This test ensures that the Hex iterator becomes empty after consuming all the bytes.

4. test_hex_iterator_not_empty_with_remaining_escaped_byte: This test checks that the Hex iterator is not empty when there are remaining escaped bytes.

5. test_hex_iterator_not_empty_with_remaining_byte: Similar to the previous test, this one checks that the Hex iterator is not empty when there are remaining unescaped bytes.

6. test_hex_iterator_empty: This test verifies that the Hex iterator is empty when the input byte slice is empty.

7. test_hex_iterator_with_single_escaped_byte: This test checks that the Hex iterator correctly handles a sequence with a single escaped byte.

8. test_hex_iterator_with_multiple_escaped_bytes: This test ensures that the Hex iterator handles multiple escaped bytes correctly.

9. test_hex_iterator_with_invalid_escape_sequence: This test verifies the behavior of the Hex iterator when an invalid escape sequence is encountered.

10. test_hex_iterator_with_no_remaining_bytes: This test checks the Hex iterator when there are no remaining bytes after iteration.

11. test_hex_iterator_with_emoji_sequence: This test validates that the Hex iterator handles an input sequence containing emojis correctly.

12. test_hex_iterator_with_chinese_hanzi_sequence: Similar to the previous test, this one checks the Hex iterator with a sequence containing Chinese characters.

These tests cover various scenarios and edge cases to ensure the correctness of the Hex iterator implementation.