tests(pcap): fix support for older tshark versions

[lrstewart]

Resolved issues:

resolves #4741

Description of changes:

Fix two issues:

• Older versions of tshark don't filter out sslv2 ClientHellos like newer versions of tshark do. s2n-tls doesn't support parsing sslv2 ClientHellos outside of TLS connections. This can lead to failures parsing ClientHellos extracted from pcaps. To solve this, I made ignoring sslv2 explicit and not dependent on version.
• Older versions of tshark have a bug in their JA3 implementation where they don't ignore grease values. See https://gitlab.com/wireshark/wireshark/-/issues/17942. This can lead to failures in the JA3 tests. To solve this, I made ja3 an optional feature.

I also made the build script sanity check that the tshark version is compatible with the features selected.

Call-outs:

Alternatively, we could just decide that the pcap tests don't support older wiresharks / older environments like Ubuntu18 and not feature gate anything. The build could just fail if tshark is too old.

Testing:

I tested manually on my ubuntu18 instance, which has wireshark 3.6.2 and can repro all these problems. I'm not convinced that it's worth adding an ubuntu18 pcap test job to the CI, but I'm very interested in other opinions.

• cargo test --features ja3:

   Compiling pcap v0.1.0 (/home/ubuntu/s2n-tls/tests/pcap)
error: failed to run custom build command for `pcap v0.1.0 (/home/ubuntu/s2n-tls/tests/pcap)`

Caused by:
  process didn't exit successfully: `/home/ubuntu/s2n-tls/tests/pcap/target/debug/build/pcap-2d5b93d1c101fc2d/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at build.rs:118:13:
  tshark >=3.7.0 required for ja3, 3.6.2 found
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

• cargo test --features ja4:

   Compiling pcap v0.1.0 (/home/ubuntu/s2n-tls/tests/pcap)
error: failed to run custom build command for `pcap v0.1.0 (/home/ubuntu/s2n-tls/tests/pcap)`

Caused by:
  process didn't exit successfully: `/home/ubuntu/s2n-tls/tests/pcap/target/debug/build/pcap-1dbfc72b0f0aae7e/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at build.rs:126:13:
  tshark >=4.2.0 required for ja4, 3.6.2 found
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

• cargo test

   Compiling pcap v0.1.0 (/home/ubuntu/s2n-tls/tests/pcap)
    Finished test [unoptimized + debuginfo] target(s) in 2.50s
     Running unittests src/lib.rs (target/debug/deps/pcap-3659d32f82ff35dc)

running 7 tests
test handshake_message::tests::multiple_handshakes ... ok
test client_hello::tests::multiple_hellos ... ok
test handshake_message::tests::tls_fragmentation ... ok
test tests::pcaps_source ... ok
test handshake_message::tests::tcp_fragmentation ... ok
test client_hello::tests::from_pcaps ... ok
test handshake_message::tests::from_pcaps ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 2.01s

     Running tests/s2n_client_hellos.rs (target/debug/deps/s2n_client_hellos-a24be8f353259326)

running 1 test
test parsing ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 1.42s

   Doc-tests pcap

running 0 tests

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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.