Network: fail to start if deprecated TLS config is present

[gerardsn]

#2877 removed the deprecated TLS config under network (moved to tls) i.e.,

strictmode: false
network:
  truststorefile: /ssl/truststore.pem
  certfile: /ssl/certificate.pem
  certkeyfile: /ssl/certificate.pem
  grpcaddr:  :5555

As this is no longer parsed, nodes using this config now try to connect to peers without TLS. This obviously fails, but the message is extremely unhelpful:

2024-03-13 11:22:56 time="2024-03-13T10:22:56Z" level=debug msg="failed to open a grpc ClientConn" error="context deadline exceeded: connection error: desc = \"error reading server preface: http2: frame too large\"" module=Network peerAddr=<rein> peerAuthenticated=false peerDID= peerID=
2024-03-13 11:22:56 time="2024-03-13T10:22:56Z" level=debug msg="failed to open a grpc ClientConn" error="context deadline exceeded: connection error: desc = \"error reading server preface: EOF\"" module=Network peerAddr=<wout> peerAuthenticated=false peerDID= peerID=
2024-03-13 11:22:56 time="2024-03-13T10:22:56Z" level=debug msg="failed to open a grpc ClientConn" error="context deadline exceeded: connection error: desc = \"error reading server preface: EOF\"" module=Network peerAddr=<gerard> peerAuthenticated=false peerDID= peerID=
2024-03-13 11:22:57 time="2024-03-13T10:22:57Z" level=debug msg="failed to open a grpc ClientConn" error="context deadline exceeded: connection error: desc = \"error reading server preface: http2: frame too large\"" module=Network peerAddr=<e-care> peerAuthenticated=false peerDID= peerID=

Solution: A node should fail to start if the deprecated config settings are present

(Nodes not wanting to use TLS still works fine as demonstrated by e2e tests)