fix(core,player,app): styled subtitles keep their size and place unless restyled

mpv's default sub-ass-override, `scale`, hands an ASS track sub-scale,
and sub-pos reaches it under every mode but `no`. So with "Restyle
styled subtitles" off, the subtitle size and position settings still
resized and moved typeset dialogue and signs.

The override is now `yes` when restyling is off, which keeps sub-scale
off ASS. A styled track also ignores the style's position, and moves
only to stay clear of the player's controls. A frame from an ASS track
rendered with every other option changed now matches the untouched one
pixel for pixel. Plain (SRT) tracks still take the whole style.

docs/FAQ.md

@@ -25,8 +25,8 @@ with hardware decoding where the device has it.
 
 Yes. In **Settings → Subtitles** you can set the size, position, font, colours, outline, box,
 shadow and blur. A **Box** background is easiest to read on bright scenes. Styled subtitles (ASS)
-keep the look their makers gave them and take only the size and position, unless you turn on
-**Restyle styled subtitles**.
+keep the look, size and place their makers gave them, unless you turn on **Restyle styled
+subtitles**.
 
 ## The subtitles are early or late.