adaptivedemux2: Prevent duplicate symbols on static builds

Fixes an issue where some mssdemux and soup symbols were duplicated in static builds.

First discovered after adding adaptivedemux2 to the Cerbero build recipe - cross-android universal examples build fails because the Android player example fails to link, reporting multiple redefinitions of mss and soup functions.

MSS symbols were simply renamed to match other symbols duplicated by adaptivedemux2 (gst_mpd_client2_* for example). libsoup related ones, since they can't just be renamed globally, have their names re#defined when being built together with adaptivedemux2 to avoid conflicts.

Example failed build: https://gitlab.freedesktop.org/seungha.yang/cerbero/-/pipelines/587605