This improves the performance of deployment, by aggregating uncached select calls for vars generate into two batches.
batch 1: Get all generators of all machines
batch 2: get all final scripts for generators which need to run
optimize the `clan vars generate` procedure by pre-caching more selectors.
To achieve this, helper functions are added to several classes.
Also a debugging feature is added to the Flake class in order to track stack traces of cache misses
fixes https://git.clan.lol/clan/clan-core/issues/3791
This fixes multiple issues we had when re-generating shared vars.
Problem 1: shared vars are re-generated for each individual machine instead of just once (see #3791)
Problem 2: When a shared var was re-generated for one machine, dependent vars on other machines did not get re-generated, leading to broken state
Reviewed-on: https://git.clan.lol/clan/clan-core/pulls/5001
- full_closure is obsolete since it is the same as calling requested_closure with the full list of generators.
- minimal_closure is obsolete as well. Since the recent addition of dependents to the closure via 3d2127ce1e it is essentially the same as the all_missing_closure
