Expose fxaa and smaa system as public for ordering constraints

[komadori]

Objective

Encountered while porting the bevy_mod_outline ecosystem crate to Bevy 0.19-dev:

Previously, bevy_mod_outline's custom rendering pass ran in between tone-mapping and the anti-aliasing post-processes. This is because outlines are conceptually outside of the world. Rendering them before tone-mapping causes them to be visually affected by other objects in the scene which makes them look like they are part of it. This was accomplished in Bevy 0.18 by adding a render graph edge between the outline render node and the Tonemapping and Fxaa/Smaa nodes. However, with the migration to render-nodes-as-systems, the fxaa and smaa systems are not public and hence cannot be referenced in system ordering constraints.

Solution

• Change the fxaa and smaa systems from pub(crate) to pub.

Testing

• Tested Bevy builds and the newly exposes systems can be referenced from an ordering constraint in a dependant crate.

[komadori]

@alice-i-cecile Is it possible to add this PR to the 0.19 milestone?