Add support for non-uniform distributions of elements

[MartinKarp]

Adds an environment variable rank_weight that can be set in order to weight the distribution of elements across ranks.

[timofeymukha]

Did we forget to review this?

[njansson]

Since everything is OO, I would argue that it should be solve by a new distribution type, and not by adding optional arguments

[timfelle]

@njansson, @timofeymukha What is the plan here?

[njansson]

@njansson, @timofeymukha What is the plan here?

I would say we can close it for now (and reopen when needed).

This was mainly for a project specific use case

[timofeymukha]

Yeah, if nobody bothered with it since Oct 2022, I think we can close it for now.