DP-7586 Improve assertions and docs

[dfkyle]

Strengthen assertions and improve RFC citations.

Skip network tests

support@docker-host-unknown:~/bgpkit-parser$ cargo clippy && OPENSSL_DIR=/usr OPENSSL_LIB_DIR=/usr/lib/x86_64-linux-gnu cargo test --quiet -- \
  --skip test_new_with_reader \
  --skip test_new_cached_with_reader \
  --skip test_filters_on_mrt_file \
  --skip test_filter_iter \
  --skip test_filter_iter_with_negation \
  --skip test_filter_iter_multi_peers \
  --skip test_negated_filters_on_mrt_file \
  --skip test_parser_as_paths_conversion \
  --skip test_record_iter_raw_record_iter_types \
  --skip test_encode_small \
  --skip test_encode_ipv6 \
  --skip test_encode_large \
  --skip test_encode_table_dump_v1
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.10s

running 460 tests
....................................................................................... 87/460
....................................................................................... 174/460
....................................................................................... 261/460
....................................................................................... 348/460
....................................................................................... 435/460
.........................
test result: ok. 460 passed; 0 failed; 0 ignored; 0 measured; 10 filtered out; finished in 1.76s


running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 2 filtered out; finished in 0.00s


running 5 tests
.....
test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s


running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 4 filtered out; finished in 0.00s


running 46 tests
iii...............iii.........................
test result: ok. 40 passed; 0 failed; 6 ignored; 0 measured; 0 filtered out; finished in 0.95s