* Join similar imports
Avoid the confusion that might cause one to think that they come from
different modules or crates.
* Create an `Arguments` helper type
A type to keep track of a list of arguments for a sub-process. It makes
it easier for overriding parameters with new values.
* Create an `args!` helper macro
Make it simpler to create `Arguments` instances with known values.
* Require `Arguments` for `spawn_child` method
Change the method to have an `Arguments` parameter, and merge it with
some default values before passing them forward.
* Use `Arguments` in `spawn_lightwalletd_child`
Change the method to use an `Arguments` instance, and merge it with some
default options.
* Use `Arguments` in `spawn_child_with_command`
Require an `Arguments` instance in the `spawn_child_with_command`
extension method. Makes it simpler to call from `spawn_child` and
`spawn_lightwalletd_child` extension methods.
* Test if argument order is preserved
Check that when building an `Arguments` instance, the order that the
arguments are set is preserved in the generated list of strings.
* Refactor test to improve readability
Also separates some common code to be reused by later tests.
* Test overriding arguments
Check to see if overriding arguments behaves as expected, by keeping the
argument order when overriding and not introducing duplicates.
* Refactor test to improve readability
Move out a chunk of code so that the test itself is easier to read and
to make that code reusable by a later test.
* Test that `Arguments` instances can be merged
Merge two `Arguments` instances built from two lists of arguments, and
check that the expanded strings preserve order and override rules.
* Add Eq derives on Arguments
Co-authored-by: teor <teor@riseup.net>