Chunk cache reimplementation

apps/arweave/include/ar_chunk_cache.hrl

@@ -0,0 +1,11 @@
+-record(ar_chunk_cache_group, {
+  chunk_cache = #{} :: #{term() => binary()},
+  chunk_cache_size_bytes = 0 :: non_neg_integer(),
+  reserved_chunk_cache_bytes = 0 :: non_neg_integer()
+}).
+
+
+-record(ar_chunk_cache, {
+  chunk_cache_groups = #{} :: #{term() => #ar_chunk_cache_group{}},
+  chunk_cache_limit_bytes = 0 :: non_neg_integer()
+}).