Implicitly capturing "this" with the capture default "=" is deprecated
with C++20. We fix this by either explicitly passing this, or by copying
the required members manually.
While this exposes some rather expensive copies like the QList
selectedItems in OBSBasic_Preview, it doesn't introduce them ("=" copies
implicitly).
"Enable network optimizations" in the Advanced Settings is referred to
as `NewSocketLoop` in the code. This feature was incompatible with
multitrack video but now works properly. Remove it from the
incompatible settings check.
