[EPIC] Move prisma 2 rust code from `prisma` repo to somewhere else

Currently the repository prisma/prisma contains the source code for Prisma 1 as well as Prisma 2. We want to move the parts written in Rust (the engines) somewhere else.

The following steps need be done to accomplish this:

• get rid of mixed mode integration tests via native-bridge
• make prisma-rs independent of the Prisma 1 server/.envrc
• separate pipelines for Prisma 1 and 2 (although still in the same repo)
• move prisma-rs to be determined location and repo

[dpetrick]

Code move is done. New repository is: https://github.com/prisma/prisma-engine.

[janpio]

@mavilein Please confirm that everything you thought of was taken care of here and just close this issue ans confirmation.