SQLStore: Prevent concurrent migrations (#44101)

* SQLStore: Prevent concurrent migrations

* Hide behind a feature toggle

* Configurable locking attempt timeout

* Update docs/sources/administration/configuration.md

Co-authored-by: Igor Suleymanov <radiohead@users.noreply.github.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/services/sqlstore/migrator/dialect.go

@@ -7,6 +7,11 @@ import (
 	"xorm.io/xorm"
 )
 
+var (
+	ErrLockDB        = fmt.Errorf("failed to obtain lock")
+	ErrReleaseLockDB = fmt.Errorf("failed to release lock")
+)
+
 type Dialect interface {
 	DriverName() string
 	Quote(string) string
@@ -53,6 +58,13 @@ type Dialect interface {
 	IsUniqueConstraintViolation(err error) bool
 	ErrorMessage(err error) string
 	IsDeadlock(err error) bool
+	Lock(LockCfg) error
+	Unlock(LockCfg) error
+}
+
+type LockCfg struct {
+	Session *xorm.Session
+	Timeout int
 }
 
 type dialectFunc func(*xorm.Engine) Dialect
@@ -288,3 +300,11 @@ func (b *BaseDialect) TruncateDBTables() error {
 func (b *BaseDialect) UpsertSQL(tableName string, keyCols, updateCols []string) string {
 	return ""
 }
+
+func (b *BaseDialect) Lock(_ LockCfg) error {
+	return nil
+}
+
+func (b *BaseDialect) Unlock(_ LockCfg) error {
+	return nil
+}