Bump Rust to 1.75 (#3815)

**This PR also bumps wasmtime version from 0.38 to 2.0 as 0.38 does not
build with Rust 1.75**. I did not test the plugin runtime as (AFAIK) we
intend to deprecate it; also, wasmtime's most recent version is 16.0, so
it'd make sense to bump the version at some point anyways. I did not
bump the version to 16.0 straight away as that'd require code changes in
`plugin_runtime`.
Release Notes:

- N/A

crates/ui2/src/ui2.rs

@@ -28,7 +28,6 @@ pub use components::*;
 pub use disableable::*;
 pub use fixed::*;
 pub use prelude::*;
-pub use selectable::*;
+
 pub use styled_ext::*;
 pub use styles::*;
-pub use visible_on_hover::*;