Add pixi as alternative to develop locally

Add pixi as alternative to build pytango locally.

Pixi manages environments for the developers and allows to define "tasks" giving a simple and unified way to work on a project whatever the platform.

It is still under active development but I think it's worth trying it. From my experience it can really simplify the developers life, abstracting the installation and management of dependencies. The pixi.toml file is in a format easy to read and that shouldn't add much maintenance.

I propose that we add it as an alternative method for now so we can try and evaluate.

I added 2 CI jobs that can be run on schedule to test some pixi commands and ensure it doesn't break when a new version of pixi is released (or we forgot to update something in the pixi.toml file).