Added file copying role option and node config option

[capnspacehook]

Added role option and node config option for controlling remote file operations via SCP/SFTP.

For #13216.

[jakule]

@capnspacehook PR looks fine. I'm just not sure why we need a new certificate extension permit-file-copying. Here is my output from tsh status

% tsh status
> Profile URL:        https://example.com:3080
  Logged in as:       bob
  Cluster:            example.com
  Roles:              admin, auto-users, disable-file-copy
  Logins:             ubuntu1, ubuntu, admin, -teleport-internal-join
  Kubernetes:         enabled
  Kubernetes groups:  edit
  Valid until:        2022-08-19 02:34:23 -0400 EDT [valid for 11h44m0s]
  Extensions:         permit-file-copying, permit-port-forwarding, permit-pty

We need permit-port-forwarding, permit-pty extensiona as OpenSSH uses them permit-port-forwarding, permit-pty permit-file-copying looks redundant.

[capnspacehook]

@jakule gotcha, I was initially using a PR that added port forwarding to guide what code I should change, didn't exactly understand what the extensions were for. I'll remove that.