remove rs2 structs from context.h

[maloel]

The rs2_device_list struct, outside of librealsense namespace, was used all the way in the device factories.

• changed device-factories to use std::vector< std::shared_ptr< device_info > > instead
• changed context::on_device_changes() to accept a callback, rather than rs2 concepts
• removed rs2_device_info and changed rs2_device_list to also use std::vector< std::shared_ptr< device_info > >
• moved rs2_device_list into rs.cpp
• moved rs2_stream_profile into stream.h until the latter is refactored, too
• removed context.h includes where not needed

Tracked on [LRS-921]

[OhadMeir]

Good job simplifying the code and cleaning unneeded includes