CLENAUP: config: move CONFIG_HAP_LOCKLESS_POOLS out of config.h

The setting of CONFIG_HAP_LOCKLESS_POOLS depending on threads and
compat was done in config.h for use only in memory.h and memory.c
where other settings are dealt with. Further, the default pool cache
size was set there from a fixed value instead of being set from
defaults.h

Let's move the decision to enable lockless pools via
CONFIG_HAP_LOCKLESS_POOLS to memory.h, and set the default pool
cache size in defaults.h like other default settings.

This was the next-to-last setting in config.h.
diff --git a/include/common/defaults.h b/include/common/defaults.h
index 3350825..aeddb01 100644
--- a/include/common/defaults.h
+++ b/include/common/defaults.h
@@ -307,6 +307,11 @@
 #define MEM_USABLE_RATIO 0.97
 #endif
 
+/* default per-thread pool cache size when enabled */
+#ifndef CONFIG_HAP_POOL_CACHE_SIZE
+#define CONFIG_HAP_POOL_CACHE_SIZE 524288
+#endif
+
 /* Number of samples used to compute the times reported in stats. A power of
  * two is highly recommended, and this value multiplied by the largest response
  * time must not overflow and unsigned int. See freq_ctr.h for more information.