Chore: Make cgo optional (for sqlite) (#108756)

* make cgo optional for sqlite

* update go.mod; check error code differently

* reduce api surface even more

* move test errors into sqlite package

* add a comment

pkg/util/sqlite/sqlite_cgo.go

@@ -0,0 +1,46 @@
+//go:build cgo
+
+package sqlite
+
+import (
+	"errors"
+
+	"github.com/mattn/go-sqlite3"
+)
+
+type Driver = sqlite3.SQLiteDriver
+
+// The errors below are used in tests to simulate specific SQLite errors. It's a temporary solution
+// until we rewrite the tests not to depend on the sqlite3 package internals directly.
+var (
+	TestErrUniqueConstraintViolation = sqlite3.Error{Code: sqlite3.ErrConstraint, ExtendedCode: sqlite3.ErrConstraintUnique}
+	TestErrBusy                      = sqlite3.Error{Code: sqlite3.ErrBusy}
+	TestErrLocked                    = sqlite3.Error{Code: sqlite3.ErrLocked}
+)
+
+func IsBusyOrLocked(err error) bool {
+	var sqliteErr sqlite3.Error
+	if errors.As(err, &sqliteErr) {
+		return sqliteErr.Code == sqlite3.ErrLocked || sqliteErr.Code == sqlite3.ErrBusy
+	}
+	return false
+}
+
+func IsUniqueConstraintViolation(err error) bool {
+	var sqliteErr sqlite3.Error
+	if errors.As(err, &sqliteErr) {
+		return sqliteErr.ExtendedCode == sqlite3.ErrConstraintUnique || sqliteErr.ExtendedCode == sqlite3.ErrConstraintPrimaryKey
+	}
+	return false
+}
+
+func ErrorMessage(err error) string {
+	if err == nil {
+		return ""
+	}
+	var sqliteErr sqlite3.Error
+	if errors.As(err, &sqliteErr) {
+		return sqliteErr.Error()
+	}
+	return err.Error()
+}

pkg/util/sqlite/sqlite_nocgo.go

@@ -0,0 +1,24 @@
+//go:build !cgo
+
+package sqlite
+
+import "modernc.org/sqlite"
+
+//
+// FIXME (@zserge)
+//
+// This non-CGo "implementation" is merely a stub to make Grafana compile without CGo.
+// Any attempts to actually use this driver are likely to fail at runtime in the most brutal ways.
+//
+
+type Driver = sqlite.Driver
+
+func IsBusyOrLocked(err error) bool {
+	return false // FIXME
+}
+func IsUniqueConstraintViolation(err error) bool {
+	return false // FIXME
+}
+func ErrorMessage(err error) string {
+	return "" // FIXME
+}