* ConnectionMultiplexer: track global counts for deebugging

* Build dammit

* Move to per-multiplexer/add tests

Note: I know mutiplexer isn't spelled right - will fix that in a follow-up to avoid noise.

* Fix test key names

Broken since the 2.1 bump, oops

* Simplify the NoConnectionAvailable static

Simpifies usage for all callers. Also shares code and adds diagnostics to the "no connection" case.

* Add tests for NoConnectionException

* Failover: fix tests and debug some

SubscriptionsSurviveMasterSwitchAsync is a thorn in our side - moving to DEBUG.

* Remove bad check

Inner is irrelevant here - can be not-null depending on the connection race.

* Update message and add more tests!

* Bump pipelines to 2.1.6