Add balances to ACS snapshots

[OriolMunoz-da]

Part of #2254

[meiersi-da]

Nice work! Computing it jointly with the snapshot sounds great. Best chance to share the work.

[moritzkiefer-da]

nice! Query plans and some timings on CILR would be great

[OriolMunoz-da]

Here's a regular explain while I fail to run the analyze on cloudsql: https://www.pgexplain.dev/plan/f4527fda-e660-4941-840a-9f1f167cac21

[OriolMunoz-da]

And here with explain analyze buffers:
https://www.pgexplain.dev/plan/1c247120-d537-436b-ab4b-3b60e09764c9#plan

^This part was pre-existing.

^For this:

• The CTE Scan of inserted_rows includes the first screenshot, (i.e., 4m are included in 5m).
• The CTE scan on creates_to_insert and the hash join are the new parts. It's... not great, but not the worst part of the query I guess

[moritzkiefer-da]

nice lgtm! Should we extend the update plugin at the end of the test to check that the balance updates are identical? Thinking about this again, I guess you're not actually exposing it over endpoints yet so this would be a follow up.

[OriolMunoz-da]

@moritzkiefer-da implemented in the last commit in #2334

[meiersi-da]

Nice! Thanks a lot!