Constants should not require 'static bound for their typeparams

[nagisa]

Code like

trait Lattice {
    const BOTTOM: Self;
}

impl<T> Lattice for Option<T> {
    const BOTTOM: Option<T> = None;
}

fails to compile (after #33572) despite being “just” all-right because compiler demands for a 'static lifetime on T, which is completely unnecessary (constants are instantiated inline).

Expected results: should compile.