Tracking issue for rustls 0.21 support

[jsha]

• ServerName can now have two kinds of value #292
• [ ] Implement client session storage #293
• sni_hostname renamed to server_name #295
• client auth type constructor changes #296
• Breaking changes in upstream error types. #297
• Update doc links for 0.21 #304

[cpu]

Here are a couple other issues that I think will need to be handled:

• sni_hostname renamed to server_name #295
• client auth type constructor changes #296
• Breaking changes in upstream error types. #297

I proposed fix patches in the first two issues (but haven't opened a PR since it's an "all or nothing" type thing to get the build green). I think I might be able to make some progress on #297 if that would be helpful.

[jsha]

Yeah, if you'd like to start in on #297 that would be great!

I'll start a rustls-0.21.0 branch to accumulate fixes.

[jsha]

Here's the initial commit on the rustls-0.21.0 branch. From here let's do pull requests against it. I intended to make this first commit a PR but accidentally pushed straight to it. I've enabled branch protection on it now.

[cpu]

@jsha Do you want to strike #293 from the burndown list based on #301 landing? It seems like leaving the issue open for future implementation might make sense but it isn't a release blocker now.

[cpu]

I made a quick branch on top of rustls-0.21.0 that integrates #305, #303, and #306 (cpu-0.21.0-smoketest) to see if CI would build 🟢.

The results were promising, only one task of the Windows CMake, Debug configuration job failed for "check static library list":

Run python tests/verify-static-libraries.py
got unexpected list of native static libraries, fix or update README: advapi32.lib credui.lib kernel32.lib secur32.lib kernel32.lib advapi32.lib userenv.lib kernel32.lib kernel32.lib ws2_32.lib bcrypt.lib msvcrt.lib legacy_stdio_definitions.lib instead of advapi32.lib credui.lib kernel32.lib secur32.lib legacy_stdio_definitions.lib kernel32.lib advapi32.lib userenv.lib kernel32.lib kernel32.lib ws2_32.lib bcrypt.lib msvcrt.lib legacy_stdio_definitions.lib
Error: Process completed with exit code [1](https://github.com/cpu/rustls-ffi/actions/runs/4502783181/jobs/7925091632#step:6:1).

[cpu]

only one task of the Windows CMake, Debug configuration job failed for "check static library list":

Here's a potential fix: #307 That was the last change required to get the branch passing.

[cpu]

We're done! 🎉

[jsha]

Yay! Thanks for all your work on this.