Replace simple_event_shunt macro with proc macro

This macro is pretty complicated and I needed to add the ability to
clean keywords, so it makes more sense to have this be a proc macro.

Cargo.toml

@@ -1,4 +1,5 @@
 [workspace]
+members = ["macros"]
 [workspace.dependencies]
 wayland-client = "0.31.2"
 wayland-protocols = "0.31.2"
@@ -35,6 +36,7 @@ xcb-util-cursor = "0.3.2"
 smithay-client-toolkit = { version = "0.19.1", default-features = false }
 
 sd-notify = { version = "0.4.2", optional = true }
+macros = { version = "0.1.0", path = "macros" }
 
 [features]
 default = []