Improve Digital Bid adapter: use the oRTB server endpoint (prebid#8138)

* Major refactoring to use new oRTB server endpoint

Co-authored-by: Faisal Islam <[email protected]>
Co-authored-by: Jozef Bartek <[email protected]>

* fixed wrong merge

* Fixed issue related to site and app (#9)

* Fixed errors for test cases.

Co-authored-by: Faisal Islam <[email protected]>
Co-authored-by: Faisal Islam <[email protected]>
Co-authored-by: Faisal Islam <[email protected]>

Author: 3 people