Bump SQL proxy to v2 so we can support multiple sql servers + deprecation of v1

[Glenn-Terjesen]

Bump SQL proxy to v2 so we can support multiple sql servers + deprecation of v1

[sindrel]

There's already support for multiple servers in v1, and it seems v1 is still being actively maintained. But we should do this bump in the not-so-far future to stay ahead: v2 has faster startup and new features like support for tracing and Prometheus metrics.

A migration guide exists at https://github.com/GoogleCloudPlatform/cloud-sql-proxy/blob/main/migration-guide.md.