$effect_chain->add() method returns array_ref containing Effect objects
append_effect(), insert_effect(), _add_effect() return array ref of Effect objects

Our idea is that when applying an effect chain,
we need to report applying multiple effects

add_effect() is a wrapper for _add_effect() that returns
a single effect ID
add_effect command reports adding multiple effects
pager type
suppress warning
adding effect chain: correctly list same-named effect chains on track