Header refactoring: tsd - cleanup and dependency breaking.

This removes the tsd macros (which are used only for tsd_t in real builds).  We
break up the circular dependencies involving tsd.

We also move all tsd access through getters and setters.  This allows us to
assert that we only touch data when tsd is in a valid state.

We simplify the usages of the x macro trick, removing all the customizability
(get/set, init, cleanup), moving the lifetime logic to tsd_init and tsd_cleanup.
This lets us make initialization order independent of order within tsd_t.

include/jemalloc/internal/rtree_externs.h

@@ -43,7 +43,5 @@ void rtree_leaf_elm_witness_access(tsdn_t *tsdn, const rtree_t *rtree,
     const rtree_leaf_elm_t *elm);
 void rtree_leaf_elm_witness_release(tsdn_t *tsdn, const rtree_t *rtree,
     const rtree_leaf_elm_t *elm);
-void rtree_ctx_data_init(rtree_ctx_t *ctx);
-bool tsd_rtree_ctx_data_init(tsd_t *tsd);
 
 #endif /* JEMALLOC_INTERNAL_RTREE_EXTERNS_H */