Add new LockManager lock types RESOURCE_DDL_DATABASE and RESOURCE_DDL_COLLECTION to be used for the new DDLLockManager.

Neither of them will be related to the engine lock hierarchy (Global > Database > Collection). However, to avoid deadlocks, none of the engine hierarchy locks has to be held when a RESOURCE_DDL_* lock is being acquired.

The advantages of having the DDL locks managed by the LockManager are:

• Enables a multi-granularity lock acquisition. This means that DDL locks could be taken in different modes: S, IS, X or IX.
• Improves the DDL locking debuggability. The DDL locks will be integrated with the already existing LockManager debug utilities.
• Code robustness. The LockManager is a relatively old and widely used service with up-and-going maintenance.