HTTPCLIENT-2096: Migrate instance loggers to static fields

Note that this may change the origin of logging when classes
have been subclassed, as the logger origin will use the class
name that defined the logger where previously the subclass type
would be used. In scenarios where external libraries subclass
httpclient utilities this allows httpclient logging to maintain
the `org.apache.hc` prefix instead of inheriting arbitrary
subclass names.

Using some logging frameworks this may result in reduced churn
when httpclient components are created (new connections, for example)
because loggers are looked up once per class.
63 files changed