move from internal TPM implementation to go-tpm-keyfile

[Foxboron]

openssl genpkey -provider tpm2 -algorithm EC -pkeyopt group:P-256 -pkeyopt user-auth:1234 -out id_ecdsa.tpm
./bin/ssh-tpm-keygen --print-pubkey ./id_ecdsa.tpm > id_ecdsa.pub
./bin/ssh-tpm-add ./id_ecdsa.tpm
ssh -i ./id_ecdsa.pub xxxxx

This works now :)