During plugin install: Don't globally deactive a package which was activated before

[passsy]

This is a rare use-case but technically possible and easy to fix.

Given package_a is globally installed.

When installing <cli> packages install package_a the package is afterwards deactivated.

sidekick/sidekick_core/lib/src/commands/plugins/install_plugin_command.dart

Lines 316 to 317 in 914bde5

	// TODO Don't deactivate when the package was already activated
	// The package was only activated to cache it and can be deactivated now

sidekick/sidekick_core/lib/src/commands/plugins/install_plugin_command.dart

Lines 210 to 214 in 914bde5

	// TODO Maybe we should do a `dart pub global list` first to check if
	// the package is already activated. If it is already activated,
	// we should at least print a warning because we are altering the
	// user's environment in a possibly unexpected way by calling
	// `dart pub global activate/deactivate`.