To validate base-level locking, we should do the following:

• Add a Decoration to Client to store a LatchSetState struct
• Make a Listener derived class that implements Mutex::LockListener and mutates the LatchSetState with onQuickLock()/onSlowLock() and onUnlock()
• Modify LockListener function signatures to take a struct Mutex::Identity that holds a name, an optional SourceLocation, and a boolean isBaseLatch. All of the contents of Mutex::Identity should be constant from Mutex construction onward.
• Change MONGO_MAKE_LATCH to construct a Mutex with a SourceLocationHolder via MONGO_SOURCE_LOCATION and isBaseLatch = false.
• Add MONGO_MAKE_BASE_LATCH to construct a similar Mutex but with isBaseLatch = true.
• Change a collection of base-level latches to be defined using MONGO_MAKE_BASE_LATCH. (See comments for potential locations)