ENH: set some sensible pixi and uv cache settings

[ZLLentz]

Description

Replace the previous branching pixi cache setup with a simple one that points pixi/uv caches to epics-dev.

Note that you also need to put your dev clones on the same disk as epics-dev to get full performance benefits.

Discussion item: is it better to put these in epics-dev, or should I create e.g. pyps-dev to keep the python and epics dev areas separate? Either way, the performance is the same. I don't know if people prefer having well-separated dev areas or if people prefer to have all their dev work in one place.

Motivation and Context

• The previous setup was under the assumption that a local disk for the pixi cache was useful and a home area cache was OK.
• Neither of these is true:
  • It's most useful to put the cache on NFS so that when you do dev with pixi the environments that are created can use hard-linking instead of copies.
  • Home area quotas are small

Therefore:

• Put the cache on a large NFS disk
• Encourage people to develop in epics-dev
• Separate cache per user so we don't clobber eachother at runtime

How Has This Been Tested?

I've been using this myself for a few days

Where Has This Been Documented?

Here only, probably warrants some sort of PSA about where to do pixi work.