Disable automatic apply-collection-filters trigger (and possible for other tasks)

[skid]

Is your feature request related to a problem? Please describe.
The apply-collection-filters job is a bit slow when you have a lot of collections. It's also triggered indiscriminately - for example if the product variant's stockOnHand changes, which has nothing to do with collections, but can be a very frequent event. This can lead to a lot of expensive jobs being run unnecessarily.

Describe the solution you'd like
It would be good to have a way to disable specific jobs, on several levels:

1. Globally - e.g. disable the apply-collection-filters hook completely and let me run it manually periodically
2. Per operation - e.g. add a method to the RequestContext that would look something like: ctx.skipJobs('apply-collection-filters'). This one is not so useful, as we can already do that if we don't use Vendure's services to do DB operations.

[michaelbromley]

Closing in favour of #1137