Memory profiling

[yaymukund]

I'm noticing [...] that the chain watcher of the customer is a little CPU heavy, or at least has a quite constant CPU load. Also, both the customer watcher and the Merchant seem to have somewhat of a memory leak, not necessarily much, but it might grow over time... I noticed the memory usage increases a bit over time. Maybe it's necessary information, but I would think that memory should stay quite stable over time given that most of the data is stored in the db anyway (and not in memory)

We can profile the memory, maybe with something like https://github.com/koute/bytehound

This was in debug mode, so we should also compare with --release performance.