Add scale `BrazilianDuration`

[musoke]

see discussion on PR for BrazilianCrux:

• https://github.com/OpenBeta/sandbag/pull/158/files#r1388446690
• https://github.com/OpenBeta/sandbag/pull/158/files#r1388568954
• https://www.cap.com.br/post/sistema-brasileiro-de-gradua%C3%A7%C3%A3o-de-vias-de-escalada

This is a new type of scale, so will require some work to identify other possible duration scales and the relations between them.

Related scales:

• NCCS commitment grade

[musoke]

@enapupe, you may have opinions on the best name for this one too

[enapupe]

Brazilian[Exposure/Duration/General] sound good to me! I think the only hard to name was BrazilianCrux 😅