Remove, revise, or replace `start_dev` target

[nmdefries]

The start_dev target is not useful. It runs bash inside a docker container, whic his easy enough to do by hand. It's also unclear which docker container it's actually trying to use.

The target runs the ghcr.io/cmu-delphi/forecast-eval image, which is meant for the dashboard, but mounts the Report and dist dirs that are only needed to run the pipeline, not the dashboard.

Three options here:

• Remove all make support for running bash in containers. Let devs do that themselves if they need to.
• Make start_dev run bash in the dashboard container only, i.e. drop pipeline dependencies. Set up another target to run bash in the pipeline forecast-eval-build image.
• Set up a variable that by default runs the dashboard or pipeline in their respective containers (start_dashboard and score_forecast), but can be overridden through the make call to run bash in each container.