Allow batched `aggregate.at` calls

[djbalin]

Proposal: Allow multiple aggregate.at calls on the same aggregate to be carried out in the same environment.

Background: Currently, each call to an aggregate/a component spins up an independent v8-isolate environment (as per Ian's statement in Discord). This means that calling aggregate.at multiple times can lead to very slow execution speeds.

Example:
In our production app, for example, the code below takes ~800 ms on a TableAggregate of approx 10,000 documents (measured by console.time):

  const indexes = [0, 1, ..., 30] // array of length = 30

  const atIndexes = await Promise.all(
      indexes.map((i) => profileSubmissionAggregate.at(ctx, i)),
   );

Note: the code above is taken from the shuffle example in the Aggregate docs: https://github.com/get-convex/aggregate/blob/main/example/convex/shuffle.ts

[ianmacartney]

This is out in an alpha if you have time to try it out - will upstream soon. sorry for the delay

[Elliot-Pitts]

Are there plans for batchSum? Would be very useful