[ENHANCEMENT] [HaCasa] - Replace old FontAwesome intergration with new one

[damianeickhoff]

The old FontAwesome integration will be deprecated. Thomas Loven has created a new integration called hass-custom-icons.

We should integrate that one and remove the old one.

[coasting24]

Be aware, he introduced a new prefix "custom:" for the custom_icons. However, the prefix "fapro:" can still be used!