Portduino: Set Web SSL Cert / Key paths from yaml

[vidplace7]

Allows SSL web certificate / key locations to be set in the meshtasticd config.yaml.

Additionally, sets the default directory for ssl storage to /etc/meshtasticd/ssl, and creates this directory in the Linux packaging.

Example:

Webserver:
  Port: 443 # Port for Webserver & Webservices
  RootPath: /usr/share/meshtasticd/web # Root Dir of WebServer
  SSLKey: /etc/meshtasticd/ssl/private_key.pem
  SSLCert: /etc/meshtasticd/ssl/certificate.pem

Resolves #5944