I removed the `static-method-test.rs` test because it was heavily based
on `BaseIter` and there are plenty of other more complex uses of static
methods anyway.
mentioned in #2625.
This change makes the module more oriented around
Process values instead of having to deal with process ids
directly.
Apart from issues mentioned in #2625, other changes include:
- Changing the naming to be more consistent - Process/process
is now used instead of a mixture of Program/program and
Process/process.
- More docs/tests.
Some io/scheduler related issues remain (mentioned in #2625).
