Which tests need to assert the lengths of exchanged messages?

Lots of our unit tests assert the lengths of various QUIC message exchanges. These kinds of tests are sensitive to changes in the configurations of the client and server in the text. For example, #2446 enables PQ key exchange by default, which adds about a KB to the ClientHello and ServerHello.

Presumably this useful for some tests, but certainly not as many as we have. We should audit which tests need this check and which don't.

Start by locating the unit tests that assert lengths of exchanged QUIC messages and review why each assertion exists. Compare checks that protect a protocol invariant with those that only reflect current client or server configuration. Done means incidental length assertions are removed while necessary checks remain, and the test suite still passes after configuration changes.

Written by the indexing model from the issue text.