This refactor is to make it easier to see how serf feature flags are
encoded as serf tags, and where those feature flags are read.
- use constants for both the prefix and feature flag name. A constant
makes it much easier for an IDE to locate the read and write location.
- isolate the feature-flag encoding logic in the metadata package, so
that the feature flag prefix can be unexported. Only expose a function
for encoding the flags into tags. This logic is now next to the logic
which reads the tags.
- remove the duplicate `addEnterpriseSerfTags` functions. Both Client
and Server structs had the same implementation. And neither
implementation needed the method receiver.
Reduce Jitter to one function
Rename NewRetryWaiter
Fix a bug in calculateWait where maxWait was applied before jitter, which would make it
possible to wait longer than maxWait.
* Implement leader routine manager
Switch over the following to use it for go routine management:
• Config entry Replication
• ACL replication - tokens, policies, roles and legacy tokens
• ACL legacy token upgrade
• ACL token reaping
• Intention Replication
• Secondary CA Roots Watching
• CA Root Pruning
Also added the StopAll call into the Server Shutdown method to ensure all leader routines get killed off when shutting down.
This should be mostly unnecessary as `revokeLeadership` should manually stop each one but just in case we really want these to go away (eventually).
Previously a sequence of events like:
Start
Stop
Start
Stop
would segfault on the second stop because the original ctx and cancel func were only initialized during the constructor and not during Start.
