time.Format() is not necessary prematurely for JSON
marshalling, since JSON marshalling indeed defaults
to RFC3339Nano.
This also ensures the 'time' is remembered until its
logged and it is the same time when the 'caller'
invoked 'log' functions.
Also log all the missed events and logs instead of silently
swallowing the events.
Bonus: Extend the logger webhook to support mTLS
similar to audit webhook target.
Logger targets were not race protected against concurrent updates from for example `HTTPConsoleLoggerSys`.
Restrict direct access to targets and make slices immutable so a returned slice can be processed safely without locks.
This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`
