Point an actor's TLS client at the MITM trust bundle by default

Currently, if MITM is enabled on a Substrate cluster, the users need to point the actor's TLS client at the MITM trust bundle by setting relative environment variables for every container in an ActorTemplate, see https://github.com/agent-substrate/substrate/blob/main/docs/egress-trust-bundle.md#point-the-runtime-at-it. This is tedious.

Should we by default inject a list of common environment variables into every container if MITM is enabled and offer users a way to opt-out this default behavior?

**Note:** currently, the users need to mount the MITM trust bundle [manually](https://github.com/agent-substrate/substrate/blob/main/docs/egress-trust-bundle.md#project-the-bundle). @thompsonmax is working on [auto-inject the egress trust volume into every actor](https://github.com/agent-substrate/substrate/pull/1252/#top).

@thompsonmax @ahmedtd @EItanya @bowei