[FEATURE] Add multi sink support to testbench

[cujomalainey]

Is your feature request related to a problem? Please describe.
Currently testbench only supports single output from process component, this makes it hard to test components that split streams like crossover

Describe the solution you'd like
Add multiple sink support to testbench

Describe alternatives you've considered
N/A all other solutions require hacking the code block under test

Additional context
@singalsu CC for input

[lgirdwood]

@ranj063 @singalsu any pointers ?

[singalsu]

@cujomalainey Superb, thanks! This has been in my wish list of things to do! I think this should be fairly straightforward to do. Maybe add support for multiple file sources too if convenient. Also feel free to clean up command line interface if needed. There's not much dependencies to fix them into scripts.

[cujomalainey]

Excellent, that is good to hear, this will allow us to better test the crossover while the UUID stuff works its way through the PR process.

[cujomalainey]

@johnylin76 this is done right?