CLEANUP: pools: rename all pool functions and pointers to remove this "2"

During the migration to the second version of the pools, the new
functions and pool pointers were all called "pool_something2()" and
"pool2_something". Now there's no more pool v1 code and it's a real
pain to still have to deal with this. Let's clean this up now by
removing the "2" everywhere, and by renaming the pool heads
"pool_head_something".
diff --git a/include/common/memory.h b/include/common/memory.h
index 311354c..5096125 100644
--- a/include/common/memory.h
+++ b/include/common/memory.h
@@ -93,23 +93,23 @@
 /*
  * This function frees whatever can be freed in pool <pool>.
  */
-void pool_flush2(struct pool_head *pool);
+void pool_flush(struct pool_head *pool);
 
 /*
  * This function frees whatever can be freed in all pools, but respecting
  * the minimum thresholds imposed by owners.
  *
- * <pool_ctx> is used when pool_gc2 is called to release resources to allocate
+ * <pool_ctx> is used when pool_gc is called to release resources to allocate
  * an element in __pool_refill_alloc. It is important because <pool_ctx> is
  * already locked, so we need to skip the lock here.
  */
-void pool_gc2(struct pool_head *pool_ctx);
+void pool_gc(struct pool_head *pool_ctx);
 
 /*
  * This function destroys a pull by freeing it completely.
  * This should be called only under extreme circumstances.
  */
-void *pool_destroy2(struct pool_head *pool);
+void *pool_destroy(struct pool_head *pool);
 
 /*
  * Returns a pointer to type <type> taken from the pool <pool_type> if
@@ -209,7 +209,7 @@
  * dynamically allocated. In the first case, <pool_type> is updated to point to
  * the next element in the list. Memory poisonning is performed if enabled.
  */
-static inline void *pool_alloc2(struct pool_head *pool)
+static inline void *pool_alloc(struct pool_head *pool)
 {
 	void *p;
 
@@ -238,7 +238,7 @@
  * pointer. Just like with the libc's free(), nothing
  * is done if <ptr> is NULL.
  */
-static inline void pool_free2(struct pool_head *pool, void *ptr)
+static inline void pool_free(struct pool_head *pool, void *ptr)
 {
         if (likely(ptr != NULL)) {
 		HA_SPIN_LOCK(POOL_LOCK, &pool->lock);