Allow Sat to use a Directive-like configuration for certain Runnable capabilities

[danielledeleo]

Currently, Sat isn't able to use all of the Runnable capabilities on its own without help from an AppSource.

[k33g]

It would be fine if we could use environment variables for the Redis connection (cache):

SAT_HTTP_PORT=8080 REDIS_HOST="" REDIS_PORT="" REDIS_PWD=""  sat ./hello-swift/hello-swift.wasm 

Use case: Registering the Runnable at the start into the RedisDb, then we can use it as a service discovery backend