fix(docdiff): fix docdiff

[toidiu]

Description of changes:

Upgrading to new rust version broke docdiff (parsing html docs). This PR fixes the doc parsing.

There have been numerous changes, which makes the diff quite large. Alot of the changes are 3rd-party libs(rustls, rust std, s2n-tls).

Call-outs:

• [ ] prior to merging we need to make sure that the diff is actually working correctly
  • Since the diff for api.snap is large!! I took the git diff of api.snap and parsed/filtered it to make the diff more consumable. see https://github.com/toidiu/docdiff_git_diff_compare for more details on the exact implementation.
• [ ] The sim crate is using an unstable feature but doesnt have conditional compilation. I did a quick fix (cfg(unstable-provider...)) to get docdiff to compile but need to make sure this works

This can now be viewed here compare/, approved and then I can remove the files in a following commit once we are happy.

Future work:

The diff is quite large and hard to decipher. I think we could benefit from smaller api.snap files. A separation could be for done for rustls, s2n-tls, and possibly different modules within s2n-quic.

Is this a refactor change? If so, how have you proved that the intended behavior hasn't changed? -->

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