live_effects/parameter/*array cleanup/optimisation

Noticed in preparing for changes to Gtk::TreeIter et al., coming in GTK4

• Qualify std::size_t.
• Replace gchar with char, or where possible auto.
• Avoid an unnecessary g_strdup().
• Consistently use std::size_t, not unsigned, to iterate by index.
• Remove redundant defaulted destructors.
• Replace in-body assignment of pointers/booleans w/ in-member defaults.
• Replace raw pointers and new/delete with std::unique_ptr.
• Replace Gtk::manage(new T) with Gtk::make_managed().
• Use auto for iterator types, slimming down some huge repetitive lines.
• Iterate over _vector of shared_ptr by const&, avoiding copy/refct inc.
• Iterate over scratch vectors of ustrings with && instead of copying...
• Move deleted special members to public in case that means better error
• Make members private that can be, not protected.
• Add some missing #includes for gtkmm widgets.
• Use auto_connection instead of manually disconnect()ing.
• Avoid unnecessary shared_ptr copy/refct incr., in Satellite::unlink().
• Deduplicate overloads of said method & vastly simplify implementation.
• Remove some widget members that aren't used outside of one function.
• Make others that we rebuild into unique_ptrs, to be clear re ownership
• Move strings and shared_ptrs into destination containers, not copying.
• Clean up un/needed #includes, forward-declarations, and namespaces.