In stable, the storyboard filename is fixed. In lazer, we were always
looking for the first `.osb` in the database. In the case a beatmap
archive housed more than one `.osb` files, this may load the incorrect
one.
Using `GetDisplayString` here feels like it could potentially go wrong
in the future, so I'm open to hard-coding this locally (or using string
manipulation to remove the ` [creator_name]` portion of the beatmap's
filename). Open to opinions on that.
Fixes storyboard playback in https://osu.ppy.sh/beatmapsets/1913687#osu/3947758
Now that just one method for stopping samples is left, let's just
repurpose st as the general "stop global effects" method rather than
have it there with a hyperspecific name. It also has good symmetry, as
there already was a `Start()` method in the class.
It is unnecessary, as a successful restart will exit the current player
screen, and `OnExiting()` has another `StopSampleAndRemoveFilters()`
call, which means that in the restart flow the sample was actually
getting stopped twice.
Standard exit flow is fine, it only stopped the sample once.