Initialize default values for viewports in rendering server.
Initialize default values for viewports in rendering server.

Example with TAA: by default it is `false` in project settings and in
the Viewport node. When the scene tree is created, Viewport.set_use_taa()
is called with the value from ProjectSettings. But because the default
values are already the same, RenderingServer isn't called.
The Viewport struct in the RenderingServer does not initialize this field,
so TAA gets randomly enabled when the game starts with default settings.

Zylann/godot,guilhermefelipecgs/godot,godotengine/godot,pkowal1982/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,vkbsb/godot,Valentactive/godot,guilhermefelipecgs/godot,josempans/godot,godotengine/godot,guilhermefelipecgs/godot,pkowal1982/godot,sanikoyes/godot,firefly2442/godot,ZuBsPaCe/godot,josempans/godot,pkowal1982/godot,pkowal1982/godot,akien-mga/godot,Zylann/godot,Shockblast/godot,Zylann/godot,josempans/godot,Shockblast/godot,guilhermefelipecgs/godot,akien-mga/godot,firefly2442/godot,sanikoyes/godot,ZuBsPaCe/godot,akien-mga/godot,Zylann/godot,Shockblast/godot,Shockblast/godot,josempans/godot,vkbsb/godot,pkowal1982/godot,Valentactive/godot,guilhermefelipecgs/godot,firefly2442/godot,BastiaanOlij/godot,godotengine/godot,BastiaanOlij/godot,Shockblast/godot,sanikoyes/godot,Valentactive/godot,pkowal1982/godot,vkbsb/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,vkbsb/godot,ZuBsPaCe/godot,firefly2442/godot,firefly2442/godot,ZuBsPaCe/godot,akien-mga/godot,godotengine/godot,godotengine/godot,guilhermefelipecgs/godot,josempans/godot,Zylann/godot,Zylann/godot,godotengine/godot,Valentactive/godot,firefly2442/godot,BastiaanOlij/godot,ZuBsPaCe/godot,vkbsb/godot,sanikoyes/godot,akien-mga/godot,ZuBsPaCe/godot,vkbsb/godot,BastiaanOlij/godot,Valentactive/godot,Valentactive/godot,akien-mga/godot,Shockblast/godot,Valentactive/godot,BastiaanOlij/godot,godotengine/godot,josempans/godot,firefly2442/godot,akien-mga/godot,sanikoyes/godot,Shockblast/godot,Shockblast/godot,sanikoyes/godot,vkbsb/godot,ZuBsPaCe/godot,godotengine/godot,akien-mga/godot,pkowal1982/godot,Zylann/godot,josempans/godot,sanikoyes/godot,pkowal1982/godot,sanikoyes/godot,josempans/godot,Zylann/godot,vkbsb/godot,BastiaanOlij/godot,Valentactive/godot,BastiaanOlij/godot,firefly2442/godot