Change `--dragon` option for `smart build` to pull from PyPI

[MattToast]

Description

We should remove the --dragon option from smart build CLI.

Justification

SmartSim no longer directly supports Dragon and does not have a Dragon based launcher. This option effectively just removes redundant options and simplifies the build process for end users.

Implementation Strategy

This should be a relatively simple pass through the smartsim._core._cli modules and removing any references to the --dragon flag in the argparser or .dragon attr on the generated namespace. If we REALLY want to preserve backward compatibility we can keep the --dragon flag as a no-op, but I would recommend removing entirely as SmartSim is at EOL and I don't think that flag is used by any current users.

[MattToast]

The Dragon launcher actually is still shipped with SmartSim, but we are manually pulling a very old release of dragon from GitHub.

Dragon is now released on PyPI, but requires a dragon-config call to utilize HSTA. It might be worth experimenting with pulling from PyPI, but I imagine changes in the dragon API may make this a non--trivial translation.