Migrate to latest prisma version

[hgwood]

This migration should not touch the client. But it should touch the deployment pipeline, since the prisma server will no longer exist.

[hgwood]

Rough roadmap

• Translate datamodel.graphql to modern Prisma model syntax
• Remove prisma and prisma-binding from dependencies
• Install @prisma/cli and @prisma/client and generate the client with prisma generate
• In multitenant.js replace the client constructor provided by prisma-binding by the client constructor from @prisma/client
• Refactor all ctx.prisma usage to modern Prisma Client API