This reverts commit a988fad9a0.
As discussed in #57725 and clarified in #57788, `SNAME` is not meant to be used
everywhere but only in critical code paths. For theme methods specifically, it
was by design that only getters use `SNAME` and not setters.
Allows configuring the MultiplayerSynchornizer in a way similar to
AnimationPlayer.
Properties are added manually, edither as plain properties, or via the
NodePath format for child nodes' properties "path/to/node:property"
relative to the MultiplayerSynchronizer root path.
Nice things to add would be:
- Moving properties up/down in the list.
- Some form of keying, autmatic filling of the replication properity
line edit.
