After the merge of https://github.com/gravitational/teleport/pull/12674 we no longer use the following configuration:
```yaml
teleport:
ca_signature_algo: "rsa-sha2-512"
```
As we now rely upon the `x/crypto` package to choose the signing algorithm (it defaults to `rsa-sha2-512`)
**Demo**
If we set `ca_signature_algo` (the value is irrelevant) and start `teleport` we get:
```shell
root@marco:/workspace# teleport start --debug
2022-06-02T09:33:58Z WARN ca_signing_algo config option is deprecated and will be ignored, we'll always default to rsa-sha2-512. config/configuration.go:348
2022-06-02T09:33:58Z INFO Generating new host UUID: b001159a-10e0-49a7-b4dc-61c73fbe9e42. service/service.go:726
...
```
Fixes#12905
This commit upgrades the version of x/crypto we use, to the current latest
`go get -u golang.org/x/crypto`
We also replaced the deprecated variables and updated the tests to match the
current default KEX Algos
The x/crypto didn't support RSA-SHA2 algos, so we developed our own algorithm
signer. This is no longer the case, and after upgrading x/crypto to 20220518 we
can safely remove the custom code we have.
From OpenSSH 8.8+, it works if we explicitly add the older algorithm
Somthing like this: `./ssh -vvv -oPubkeyAcceptedAlgorithms=+ssh-rsa-cert-v01@openssh.comteleportadmin@moon.marco.mydemo`
* hsm: migrate CA storage schema
Migrate types.CertAuthorityV2 schema according to
https://github.com/gravitational/teleport/blob/master/rfd/0025-hsm.md#backend-storage
Includes proto changes, types.CertAuthority wrapper changes and data
migration.
Note that we keep and update the old fields for backwards-compatibility.
If a cluster is upgraded to v7 and then downgraded back to v6,
everything should keep working.
* Address review feedback
Jakub Nyckowski