Add default Stock in Data Install

[maghamed]

Currently, Inventory module installed with an absence of Stocks. It's incorrect because merchant needs to have some "Default" Stock 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 Stock created. Pre-fill data for Default Stock.
to check that after Magento Installation Default Stock 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