Deprecates functions that use wall-clock time, so that code must be explicit about what time source is used. Idiomatic usage is:
open! Require_explicit_time_source
or, in an import.ml:
include Require_explicit_time_source
module From_kernel = Async_kernel.Async_kernel_private.Require_explicit_time_source
module type Require_explicit_time_source : sig ... end