Unify graphics & ancestry for RS485 transceivers

Currently there are simple style and graphical style symbols for RS485 (half-duplex) transceivers.

This change makes them derive from a single common ancestor, using the graphical symbol type. This only applies to standard-layout 8-pin RS485 half-duplex transceivers.

While at it, I derived some duplicated symbols from the common ancestor LTC2850xS8. I have not ensured everything derives from that specific part, I only changed it when it didn't look right.

For the common ancestor LTC2850xS8, I also fixed the description: in order to be able to search for half-duplex with dash, the description or the keywords need to have the dash version.

Simple style:

Graphical style: