Lift const values to compiletime with `typenum`

[Ben-PH]

Const generics are quite restrictive in what you can do with them, and integrating them into reverse dependencies. This PR refactors the use of const generics to use types that encapsulate integer behavior, where choice of value is a one-time choice at compile time.

From a technical standpoint, this PR should be ready to go, however from a documentation standpoint, there is stull much missing:

• typenum ergonomics: I personally take the use of typenum interface for granted, but appreciate that it's not considered ergonomic by everyone. I would like to give another pass or two to make sure that only the simplest of interface usage is needed, and it falls into a really easy, intuitive form of use.
• migration efforts: For many reverse dependencies, the use of typenum will come as a surprise and maintenance burden. I would like to add migrations guides, as well as fire off a notification of some sort to all reverse dependencies. I would be willing to directly assist any project migrating to the v0.4.0 typenummed version, and will be actively seeking out the larger, more complex projects.
• defend the change: This is a significant design change, and I anticipate a constructive back/forth discussion before anything changes.

In my personal project, const generics have reared their ugly head when trying to use fugit. Instead of keeping these changes to myself, I present these changes upstream for your consideration, and if it is agreed to by the community, adoption.

Thank you.

[burrbull]

Edit by korken89: Manners please.

[Ben-PH]

EDIT: After learning from korken

The original comment is available in GitHub's edit box, no need to reiterate.

[korken89]

@Ben-PH The original comment is available in GitHub's edit box, no need to reiterate.