Remove conda.models.dist.Dist usage

[mbargull]

Summary

Tracking issue to purge Dist from conda-build.

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Motivation

A couple of days ago I got a bit annoyed by conda-build's slow (and memory intensive) ramp up before it gets to its actual first environment solving.

The mayor underlying issue is of course conda's continued use of auxlib entities for everything in the package index.
(auxlib is actually not too bad conceptually -- but it's only viable for a few thousand (top-level) entries; and a conda-forge repodata with linux-64+noarch is past half a million records by now...)
Fixing that (=IMO, move the whole object creation/validation to compiled code) would be a thing I'd welcome much; but it's also a major endeavor to tackle.

An orthogonal thing to do in conda-build is to work on purging legacy behavior/code such that we could at least prepare to make use of the deferred creation of package records.
A first step in that direction would be to finally remove conda-build's usage of the old Dist objects (removed from conda's core workings in 2018).

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Impact

• Prepare usage of newer/more performant package index handling in conda-build.
• Removal and possible removal tech debt not only in conda-build but also conda.
• Breaking changes for library uses of conda_build:
  • not only might we remove Dist-related functions which might be used downstream,
  • but also not using a Dist-based package index anymore could break downstream expectations.

Since this introduces these breaking changes, a major version bump seems sensible.

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Progress

I started to work in this 2 days ago and made good progress.
Half way through it, I noticed some defunct or unused functions/parts.
Turns out a few of them have been defunct for years, and apparently @kenodegard recently made some preparations to lessen/remove usage of Dist 🎉.
I'll open a draft pull request in the next days.

Tasks

Preview Give feedback

1. Update conda inspect channels #5033
   cla-signed locked +2
   
2. Deprecate conda.models.dist.IndexRecord #5032
   cla-signed locked +2
   
3. conda#5708 cleanup #5031
   cla-signed locked +2
   

[kenodegard]

Xref conda/conda#13192

[kenodegard]

Since this introduces these breaking changes, a major version bump seems sensible.

FYI #5064