Better error message when env vars aren't set in CI

[jaclarke]

If the env vars needed for the client to connect aren't set in CI/whatever deploy platform, then edgedb-js currently shows the Found edgedb.toml but project is not initialized. Run 'edgedb project init'. error message, which is misleading.

Instead if we can detect we're in CI, then the error message should have instructions for configuring the env vars (EDGEDB_INSTANCE+EDGEDB_SECRET_KEY for cloud, or probably EDGEDB_DSN for self hosted).