chore: run macOS, windows, and race tests with Postgres in CI (#15520)

This PR is the second in a series aimed at closing
https://github.com/coder/coder/issues/15109.

## Changes

- adds `scripts/embedded-pg/main.go`, which can start a native Postgres
database. This is used to set up PG on Windows and macOS, as these
platforms don't support Docker in Github Actions.
- runs the `test-go-pg` job on macOS and Windows too
- adds the `test-go-race-go` job, which runs race tests with Postgres on
Linux

scripts/embedded-pg/main.go

@@ -0,0 +1,76 @@
+// Start an embedded postgres database on port 5432. Used in CI on macOS and Windows.
+package main
+
+import (
+	"database/sql"
+	"flag"
+	"os"
+	"path/filepath"
+
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
+)
+
+func main() {
+	var customPath string
+	flag.StringVar(&customPath, "path", "", "Optional custom path for postgres data directory")
+	flag.Parse()
+
+	postgresPath := filepath.Join(os.TempDir(), "coder-test-postgres")
+	if customPath != "" {
+		postgresPath = customPath
+	}
+
+	ep := embeddedpostgres.NewDatabase(
+		embeddedpostgres.DefaultConfig().
+			Version(embeddedpostgres.V16).
+			BinariesPath(filepath.Join(postgresPath, "bin")).
+			DataPath(filepath.Join(postgresPath, "data")).
+			RuntimePath(filepath.Join(postgresPath, "runtime")).
+			CachePath(filepath.Join(postgresPath, "cache")).
+			Username("postgres").
+			Password("postgres").
+			Database("postgres").
+			Encoding("UTF8").
+			Port(uint32(5432)).
+			Logger(os.Stdout),
+	)
+	err := ep.Start()
+	if err != nil {
+		panic(err)
+	}
+	// We execute these queries instead of using the embeddedpostgres
+	// StartParams because it doesn't work on Windows. The library
+	// seems to have a bug where it sends malformed parameters to
+	// pg_ctl. It encloses each parameter in single quotes, which
+	// Windows can't handle.
+	// Related issue:
+	// https://github.com/fergusstrange/embedded-postgres/issues/145
+	paramQueries := []string{
+		`ALTER SYSTEM SET effective_cache_size = '1GB';`,
+		`ALTER SYSTEM SET fsync = 'off';`,
+		`ALTER SYSTEM SET full_page_writes = 'off';`,
+		`ALTER SYSTEM SET max_connections = '1000';`,
+		`ALTER SYSTEM SET shared_buffers = '1GB';`,
+		`ALTER SYSTEM SET synchronous_commit = 'off';`,
+		`ALTER SYSTEM SET client_encoding = 'UTF8';`,
+	}
+	db, err := sql.Open("postgres", "postgres://postgres:postgres@127.0.0.1:5432/postgres?sslmode=disable")
+	if err != nil {
+		panic(err)
+	}
+	for _, query := range paramQueries {
+		if _, err := db.Exec(query); err != nil {
+			panic(err)
+		}
+	}
+	if err := db.Close(); err != nil {
+		panic(err)
+	}
+	// We restart the database to apply all the parameters.
+	if err := ep.Stop(); err != nil {
+		panic(err)
+	}
+	if err := ep.Start(); err != nil {
+		panic(err)
+	}
+}