Extend the client state management to generate a hardware attestation
key if none exists.
Extend MapRequest with HardwareAttestationKey{,Signature} fields that
optionally contain the public component of the hardware attestation key
and a signature of the node's node key using it. This will be used by
control to associate hardware attesation keys with node identities on a
TOFU basis.
Updates #31269
Signed-off-by: Patrick O'Doherty <patrick@tailscale.com>
1df3b31461