Rename some shared memory initialization routines

To make them follow the usual naming convention where
FoobarShmemSize() calculates the amount of shared memory needed by
Foobar subsystem, and FoobarShmemInit() performs the initialization.

I didn't rename CreateLWLocks() and InitShmmeIndex(), because they are
a little special. They need to be called before any of the other
ShmemInit() functions, because they set up the shared memory
bookkeeping itself. I also didn't rename InitProcGlobal(), because
unlike other Shmeminit functions, it's not called by individual
backends.

Reviewed-by: Andreas Karlsson
Discussion: https://www.postgresql.org/message-id/c09694ff-2453-47e5-b26c-32a16cd75ce6@iki.fi

src/backend/storage/ipc/procarray.c

@@ -370,7 +370,7 @@ static inline FullTransactionId FullXidRelativeTo(FullTransactionId rel,
 static void GlobalVisUpdateApply(ComputeXidHorizonsResult *horizons);
 
 /*
- * Report shared-memory space needed by CreateSharedProcArray.
+ * Report shared-memory space needed by ProcArrayShmemInit
  */
 Size
 ProcArrayShmemSize(void)
@@ -415,7 +415,7 @@ ProcArrayShmemSize(void)
  * Initialize the shared PGPROC array during postmaster startup.
  */
 void
-CreateSharedProcArray(void)
+ProcArrayShmemInit(void)
 {
 	bool		found;