Remove checkpoints from extension

[mattseddon]

Follow up to #3577

Remaining items

• Update remaining screenshots from walkthrough
• Remove checkpoint logic from experiment collection code (extension/src/experiments/model/collect.ts)
• Remove override revision logic from plots (replace short sha with experiment name for calling CLI).
• Remove checkpoint type from ExperimentType enum
• Final sweep for "patches/redundancy"

[mattseddon]

I will start on the prerequisites for integrating iterative/dvc#9170

[mattseddon]

One thing that I have noticed from working on #3665 is that we inconsistently display an experiment's rev/name and commit/branch's (aka baseline's) name/sha/commit message. Here are the places where we show this information:

Experiments tree

Experiments table

Plots Ribbon

Plots image comparison table header

I think we should make an update. My proposal is that in the examples above scaly-puds would always be first with adde938 de-emphasized as secondary text (i.e match the ribbon's style). I think it makes sense to do this because we have removed checkpoints and the ability to see multiple "revs" per experiment.

@dberenbaum @shcheklein WDYT?

[mattseddon]

Realised that I missed at least one more place from the above comment.

Quick Picks

Looking at the bigger picture:

CLI

Studio

Whatever the decision I think we should standardise across all of the three products. That probably means that we want to change the Plots Ribbon for now.

[mattseddon]

Updating screenshots will be handled in #3434