Reduce metric cardinality

[lucasmo]

Takes the monolithic hub.request metric and splits it into four different metrics:

• hub.request.api.channel: all exposed api hub calls that work with channels
• hub.request.api.nonchannel: all exposed api hub calls that work on things that don't have channels (webhooks, "gui" interaction, etc)
• hub.request.internal.channel: all internal api calls that work with channels (spoke store stuff, mostly)
• hub.request.internal.nonchannel: all other internal api magic

I wasn't able to get tests running on my local workstation, so there aren't tests here 😦 That being said, this is a hard thing to test.

[lkemmerer]

I was getting started on refactoring the MetricsRequestFilter so that it's testable for the new behavior. Want me to take your branch and run with it?

[lucasmo]

I was getting started on refactoring the MetricsRequestFilter so that it's testable for the new behavior. Want me to take your branch and run with it?

@lkemmerer please do!

[lucasmo]

I'm also not set on these metric names or this quadchotomy.