This change also makes the timers implementation closer to the spec, and
sets up the stage to implement AbortSignal.timeout() (whatwg/dom#1032).
Fixes #8965
Fixes #10974
Fixes #11398
These are confusing. They say they are "for users that don't care about
permissions", but that isn't correct. `NoTimersPermissions` disables
permissions instead of enabling them.
I would argue that implementors should decide what permissions they want
themselves, and not take our opinionated permissions struct.
