Endpoint config should not be overwritten by Zenoh config file

[oteffahi]

Describe the bug

Some link configurations can either be passed by endpoint parameters or via the zenoh config file. Currently the config file is given priority over endpoint parameters, which shouldn't be the case. Config file should be a fallback if no config is given on the specific endpoint.

To reproduce

1. Create a zenoh config file with TLS config.
2. Set transport/link/tls/enable_mtls to true.
3. Set listen/endpoints to ["tls/[::]:7447#enable_mtls=false"]
4. Start a peer/router with the config file, connect to it with a client via tls and notice how mtls is enabled.

System info

Zenoh 1.0.4