Add default Source in Data Install.

[naydav]

Currently, Inventory module installed with an absence of Sources. It's incorrect because merchant needs to have some "Default" Source to deal with, as it's implemented in Single Stock Magento.
Read this document for more details - https://github.com/magento-engcom/msi/wiki/The-Concept-of-Default-Source-and-Domain-Driven-Design

What we need to do is:

to Add Install data with default Source created. Pre-fill data for Default Source.
to check that after Magento Installation Default Source added. Cover this behavior with Integration test.

*In case of any questions - send an email to engcom@magento.com, or ask a question in #MSI Slack channel