add tests that cause decoding to panic

[0xalpharush]

---- test_c stdout ----
thread 'test_c' panicked at /Users/x/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bytes-1.8.0/src/lib.rs:138:5:
advance out of bounds: the len is 10 but advancing by 16

---- test_a stdout ----
thread 'test_a' panicked at sszb_derive/tests/tests.rs:31:28:
mid > len
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- test_b stdout ----
thread 'test_b' panicked at sszb_derive/tests/tests.rs:31:28:
attempt to subtract with overflow

[ghiliweld]

good looks, thanks for flagging @0xalpharush!