This commit replaces all TLS connection code with wolfssl.
The certificate parsing code has to remain for now, as wolfssl does not
seem to have any exposed API for that.
This allows the decoder to fail gracefully when reading a partial or
malformed TBSCertificate. We also now ensure that the certificate data
is valid before making a copy of it.
Using a file(GLOB) to find all the test files in a directory is an easy
hack to get things started, but has some drawbacks. Namely, if you add
a test, it won't be found again without re-running CMake. `ninja` seems
to do this automatically, but it would be nice to one day stop seeing it
rechecking our globbed directories.
