Add hidden config to disable pin/unpin monitoring
Merge pull request #2868 from chrisvest/2.2-hidden-config-for-pagecache-pinunpin-monitoring

Add hidden config to disable pin/unpin monitoring
Fix races on shutdown in Muninn

The Muninn eviction thread did not anticipate that closing the page cache would
set all the MuninnPage references in the `pages` array to `null`, and so it
could die with a NullPointerException.

It now interprets the precense of a `null` value as a signal to shut down.
Merge pull request #2876 from davidegrohmann/2.2-fix-muninn-shutdown-races

Fix races on shutdown in Muninn
Ensure nodes of argument relationships are planned correctly

Simplified examples (assumes no squashing):

o MATCH (a)-[r]-(b) WITH r MATCH (p)-[r]-(q) needs to project p, q from r
o MATCH (p)-[r]-(q) WITH p AS a, q AS b, r MATCH (a)-[r]-(b) needs to filter out r where a, b are not start and end nodes resp.
Rename UnwindPlan => UnwindCollection
Introduce ProjectEndpoints plan and pipe

o Introduce QueryContext.relationship(Start|End)Node
o Tests for ProjectEndpointsPipe
Replace planArgumentRelEndpoints with newly introduced projectEndpoints step