Use native database upsert for MySQL

[rothfels]

Problem

Prisma support for native SQL upserts was recently added for CockroachDB, PostgreSQL, SQLite.

Equivalent functionality has not yet been added for the MySQL datasource.

previous discussion

Suggested solution

Use the same rules for choosing native MySQL upserts as for PostgreSQL etc, but use MySQL ON DUPLICATE KEY syntax.

[mdatsev]

+1. ran into the same race condition because of this

[celso-alexandre]

In the company I work in we used prisma from the start, so I remember the time when postgres suffered from te same problem in prisma 2 (if I remember correctly). But I would really like to see this working propperly in mysql too. I know mysql isn't the main connector, but I'd really love to see it implemented.