Design select-mode for the config list window

[dasupradyumna]

Context

An interactive selection mode would be needed for the plugin floating window displaying the list of all defined task configurations. This mode would allow the user to navigate the configurations, delete them and launch them using the specified keymaps. These keymaps will be configurable by the user via the plugin settings.

Proposal

Define behaviors to delete a config from the runtime config list, and to launch a task using task::run() function by passing the selected task configuration to it as argument.
Define configurable keymaps for these behaviors in this plugin floating window, called launcher UI from now on.

[dasupradyumna]

Replace LaunchTask and LaunchDebugger commands with Launch command that opens this launcher UI, after the behaviors have been defined.