It represents which probe the _thing_ was seen from, but in many cases
(container images, deployments, replicasets, services), it may have come
from several probes. We have previously conflated it to determine which
host a thing _lives on_, which it may not even have (deployments,
replica sets, services), or it may have multiple (container images).
The idea is to separate those two usages. We should convert HostNodeID
to a set of HostNodeIDs, and use that to determine which probes have
reported the thing. For determining which host a thing lives on we
should use the Parents field which we already have, but might need
extending to handle Endpoints/etc...
Squash of:
* We have to keep all the container hostnames until the end so we can
count how many we've filtered
* Adding tests for ContainerHostnameRenderer and PodServiceRenderer with
filters
* Because we filter on image name we need the image name before
filtering
* Alternative approach to passing decorators.
* Refactor out some of the decorator capture
* Don't memoise decorated calls to Render
* Fixing filtered counts on containers topology
Tricky, because we need the filters to be silent sometimes (when they're
in the middle), but not when they're at the top, so we take the "top"
filter's stats. However, this means we have to compose all
user-specified filters into a single Filter layer, so we can get all
stats.
There are no more Silent filters, as all filters are silent (unless they
are at the top).
Additionally, I clarified some of the filters as their usage/terminology
was inconsistent and confused. Now Filter(IsFoo, ...) *keeps* only nodes
where IsFoo is true.
