VLC 2.2.x fully controlled VLCs audio or videofilter-related config
variables with the filter dialogs and the video or audio effects
panel overwrote any changes from config with the values from the
panel.

In VLC 3.0, the config is left alone and filter parameters
are only read from the preset strings. Additionally, by default
the Default profile (with default off settings) will be loaded at
startup, to ensure that no filters accidentially stay enabled.

Therefore, for migration, from 2.2.x to 3.0 versions, lets clear
the audio-filter and video-filter variables. Users with custom
profiles still keep their settings.

close #19260

(cherry picked from commit 31140f02

)
Signed-off-by: David Fuhrmann <dfuhrmann@videolan.org>