stream_bluray: cache current playback informations

The cost of calling bd_get_title_info() is quite expensive and
requires lots of CPU usage. Using BD_EVENT_PLAYLIST and
BD_EVENT_TITLE, it's possible to cache BD_TITLE_INFO object for
current title and BD_EVENT_ANGLE handler caches current angle. In
my test case, with this commit, CPU usage can be saved about 15-20%.
stream_bluray: use bd_get_playlist_info()

Use bd_get_playlist_info() instead of bd_get_title_info(). The
previous implementation couldn't query current playlist and this
made it impossible to call bd_get_playlist_info() which is more
desirable than bd_get_title_info() because, for Blu-rays, playlist
is the unit of playback not title. This commit fixes that.