fix: getConfigDefaultAccount

[kemmerle]

Description and Context

While working on #1273, I discovered that getConfigDefaultAccount was mistakenly being passed a config argument in a number of places. In fact, it takes zero arguments. This also had implications for the selectAccountFromConfig and deleteSandboxPrompt functions, both of which were being passed config unnecessarily to pass to getConfigDefaultAccount.

This PR removes a bunch of code. If you'd like to test out the changes, the impacted commands are:

hs accounts use
hs accounts list
hs accounts remove
hs auth
hs sandbox delete

TODO

• Address feedback

Who to Notify

@brandenrodgers @camden11 @joe-yeager