[CLI] Changed default nix bash to bashInteractive

[mohsenari]

Summary

In shellPath() function where we decide which type of shell to use when dropping user in devbox shell, if we can't figure out the shell, we drop the user in the default bash that nix installs in store. But this bash doesn't handle arrow keys and keyboard combinations very well, so it creates a frustrating experience for users (including pure shell users). bashInteractive package has all these capabilities and makes the experience better for a 'default' shell.

So this PR changes this:

• nix eval <bash> to get store path and use to create default shell
  to this:
• nix eval <bashInteractive> to get store path
• nix build
• use store path to create default shell

Addresses #1193

How was it tested?

• compile
• ./devbox shell --pure
  OR
• unset $SHELL
• ./devbox shell

[mikeland73]

Thoughts on using devbox.addDevboxUtilityPackage instead? It installs in a specific profile. (not sure if that works with bashNixStorePath)

[mohsenari]

@mikeland73 I tried and it works, I had to pass just the package name (bashInteractive) but the issue is it shows bashInteractive: success every time you go to a pure shell.
see:

➜  shellpure2 ./devbox shell --pure
Starting a devbox shell...
bashInteractive: Success
Welcome to devbox!
(devbox) Mohsen-Ansaris-MacBook-Pro:shellpure2 mohsenansari$

I spoke with John and the preference is to not show the install message every time and only show it if we're installing for the first time to explain the delay in shell start time. Which I can do a follow up PR for that.