refactor(core): Centralize scaling mode (no-changelog)

[ivov]

No description provided.

[krynble]

General direction is looking good.

I was thinking if we could leverage ActiveExecutions' existing functionality as part of the Worker.ts's runningJobsSummary but that could be just an enhancement for the future.

[krynble]

Hopefully we can get rid of all the watchdog functionality

[netroy]

I think we should do this in 2 parts:

• part 1 should be the refactor that reorganizes most of our existing code in packages/cli/src/scaling-mode in a way that we can also add lots of unit tests for
• part 2 is when we actually make the switch. This should be in v2.

It's entirely possible that we might be able to address some of the issues without the bullmq upgrade, by simply moving away from the super-entangled code that the current worker stuff is.