allows local tracer's push config to be read from env variables

[staheri14]

Currently, the push configuration of the local tracer requires a JSON file containing the credentials for pushing operations. However, in the context of knuu test, it has been suggested to handle these credentials as environment variables rather than as a file. This approach ensures that the credentials persist only as long as the container process is running and are eliminated once the container stops. This reduces the risk of data persistence. Conversely, when credentials are stored in a file, there is a risk that they may persist beyond the lifecycle of the container. This could lead to credential leakage if the storage is reused or accessed by other processes.

Acceptance criteria

Extending the current local tracing pushing configuration by allowing configs to be read from env variables as well. Note that it won't replace the current behaviour i.e., reading from a json file, it merely enables another method to pass the credentials.