Add option to `supabase functions deploy` to delete non-local functions

When supabase functions deploy is run, any functions present on the cloud that aren't present in your local development environment are kept. This obviously has uses in many cases, but sometimes deploying exactly what your local environment has is useful (such as in test envs). Having to remember to manually delete functions from each environment after each change isn't ideal, and leaving older, legacy functions available on your app may pose security or data risks.

You can create a script to achieve this by listing out your cloud & local functions and determining which ones to delete; however, a straightforward built-in flag would be much simpler and less error-prone (supabase functions list isn't simple to parse).