Increase number of long build slots

[carlocab]

Now that Sequoia bottling is largely complete for arm64, let's increase
the number of long build slots again.

Instead of increasing the number of dispatch build slots to the same
number, let's decrease it instead. This guarantees that 1/4 of our
orchestrator-managed runners are always available to PRs.

[Bo98]

Thoughts on instead of a dispatch limit we continuously tweak that we instead just lower the priority of dispatch jobs to be behind PR jobs?

[carlocab]

Thoughts on instead of a dispatch limit we continuously tweak that we instead just lower the priority of dispatch jobs to be behind PR jobs?

We could do that, but we'd probably tweak that for mass bottling anyway because I don't think it should be lower priority than PR jobs then -- something similar to this (higher priority, but limited slots) sounds better for mass bottling.

[carlocab]

Merging now since long builds are stuck queueing with no other jobs running. Happy to change this to something better later.

[Bo98]

We could do that, but we'd probably tweak that for mass bottling anyway because I don't think it should be lower priority than PR jobs then

We tell everyone not to not swamp the queue so PRs can get through so raising the priority of PRs would mean we don't need to manually watch the queue as much.

[carlocab]

We tell everyone not to not swamp the queue so PRs can get through so raising the priority of PRs would mean we don't need to manually watch the queue as much.

Not sure why we're doing that, tbh. We shouldn't need to watch the queue given the fixed number of slots.