SE-0450: Package traits

[mishal_shah]

[Accepted with modifications] SE-0450: Package traits

The review of SE-0450: Package traits ended on Nov 7th, 2024, and the core team has decided to accept the proposal with modifications. Feedback on the proposal was overwhelmingly positive. The section regarding "Allowed Characters for Trait Names" has been revised to eliminate the following two requirements: The first character must be a Unicode XID start character (most letters), a digit, or _. Subsequent characters must be a Unicode XID continue character (a digit, _, or most letters), -, …