(re)activate an environment when manifest.toml is edited.

We need to show a popup before (re)activating.

To (re)activate the environment we should run something like `eval $(flox activate --dir ...)` but that has currently some bugs (env variables not being updated) and we would also handle restarting of the services.

For now, we should add a checkbox to do a "full" activate of the environment (reopening it).