add a `wait-ready` command for tapd and litd

We need an equivalent of `wait-ready` for tapd and litd.

For example, as it is right now, we can try to upload a tapd macaroon to kubernetes secrets and when it does not exist, it seems `lndinit` just hangs because of https://github.com/lightninglabs/lndinit/issues/68 .

Start by locating the existing `wait-ready` command and its command entry point, then trace how readiness is checked for other daemons. Determine how equivalent checks should work for tapd and litd, including the Kubernetes-secret case described here. Done means callers can wait for either daemon to be ready instead of lndinit hanging when the macaroon is absent.

Written by the indexing model from the issue text.