Consider using `rustls-native-certs` for fallback

I've built a Docker image containing only the CLI binary and got this:

```
[I] py: edgedb-pkg /t/d/dockerctx
$ docker run -it --rm edgedb-cli
[2022-11-17T19:06:48Z WARN edgedb::version_check] Cannot check for updates: failed to fetch JSON at URL: https://packages.edgedb.com/archive/.jsonindexes/x86_64-unknown-linux-musl.nightly.json: error sending request for url (https://packages.edgedb.com/archive/.jsonindexes/x86_64-unknown-linux-musl.nightly.json): error trying to connect: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:1919: (unable to get local issuer certificate): error trying to connect: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:1919: (unable to get local issuer certificate): error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:1919: (unable to get local issuer certificate): error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed:ssl/statem/statem_clnt.c:1919:
edgedb error: ClientNoCredentialsError: no `edgedb.toml` found and no connection options are specified
Hint: Run `edgedb project init` or use any of `-H`, `-P`, `-I` arguments to specify connection parameters. See `--help` for details
```

Ideally we should fallback to a bundled certificate store if the system store cannot be found. We seem to already depend on [rustls-native-certs](https://crates.io/crates/rustls-native-certs), so it should be a matter of actually using it.