Fixtures to generate mock data for clean up use_swap handling

[leewujung]

@lsetiawan : in this PR you'll find functions that generate mock data for testing the use_swap functionality for #1179.

I made it such that the output is in identical format with parser.ping_data_dict, for timestamp, power, and angle.

See my comment here for more info: #1179 (comment)

Because of the possible variations, I think using both the actual data for integration tests and mock data for unittest will be a good idea.

In terms of actual .raw data that we need to handle, see my previous investigation #489 (comment) and #489 (comment).

[leewujung]

BTW, the tests WILL fail because I only did the short-circuiting to make it easy to see how data looks like without the zarr_datagrams business. I did not try to fix anything downstream, because they need to be removed.

[lsetiawan]

Merged in #1185