Enable per-tcache tcache_max

1. add tcache_max and nhbins into tcache_t so that they are per-tcache,
   with one auto tcache per thread, it's also per-thread;
2. add mallctl for each thread to set its own tcache_max (of its auto tcache);
3. store the maximum number of items in each bin instead of using a global storage;
4. add tests for the modifications above.
5. Rename `nhbins` and `tcache_maxclass` to `global_do_not_change_nhbins` and `global_do_not_change_tcache_maxclass`.

include/jemalloc/internal/tcache_structs.h

@@ -55,6 +55,8 @@ struct tcache_slow_s {
 
 struct tcache_s {
 	tcache_slow_t	*tcache_slow;
+	unsigned	tcache_nhbins;
+	size_t		tcache_max;
 	cache_bin_t	bins[TCACHE_NBINS_MAX];
 };