[BUG] Memory usage increases during long runs or block synchronization

[YoshihitoAso]

Describe the bug

In our environment, if a Quorum node runs for a long time without restarting it, memory usage gradually increases and in some cases OOM occurs.
There also seems to be an issue with memory usage increasing rapidly during block synchronization. The graph below shows the memory usage when block synchronization is stopped for a certain period of time and then resynchronized. There is no noticeable increase in memory usage after the synchronization is complete.

The reason why the usage rate suddenly decreased after increasing rapidly is because the node was restarted once at this point.

Additional context

Common causes for these problems may be related to the following issues:

• Memory usage of non-validator nodes grows indefinitely, leading to OOM and unclean shutdown Consensys/quorum#1660