Improve ThreadPoolScheduler.cue behaviour when Inf/-Inf/NaN is passed
Improve ThreadPoolScheduler.cue behaviour when Inf/-Inf/NaN is passed

- If Inf is passed to :at/:in/:every, the method will never invoke the
block passed, but will return a Cancellation anyway
- If -Inf is passed, the method will invoke the block as soon as
possible and return a Cancellation
- If NaN is passed, the method will throw an exception

This also ensures a Cancellation is always returned from the dispatchers
for .cue that are supposed to be returning them, since calling it with
:every as an argument would sometimes return a List instead.

nbrown/rakudo,salortiz/rakudo,softmoth/rakudo,salortiz/rakudo,MasterDuke17/rakudo,labster/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,nbrown/rakudo,rakudo/rakudo,salortiz/rakudo,labster/rakudo,tony-o/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,nbrown/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,nbrown/rakudo,tbrowder/rakudo,rakudo/rakudo,tony-o/rakudo,tony-o/rakudo,tony-o/rakudo,nbrown/rakudo,softmoth/rakudo,rakudo/rakudo,labster/rakudo,tbrowder/rakudo,rakudo/rakudo,softmoth/rakudo,nbrown/rakudo,labster/rakudo,softmoth/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,MasterDuke17/rakudo,softmoth/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo