BACKEND: Make it possible to override global options by backend specific arguments

[HenrikBengtsson]

Make it possible to control future-related options per backend. For example,

plan(multisession, workers = 4L, wait.interval = 0.01)

would make all (multisession) futures to wait 0.01 seconds between pools, instead of the default

getOption("future.wait.interval", as.numeric(Sys.getenv("R_FUTURE_WAIT_INTERVAL", "0.2")))

This could be done by making wait.interval an argument to and a field of the Future().

See also

• https://github.com/HenrikBengtsson/future.apply/issues/41#issuecomment-535581882

[HenrikBengtsson]

Another example is from Issue #197;

plan(sequential, globals.maxSize = Inf)