[JENKINS-35184] Servlet API dependent bits in a inner-class (#2551)

* [JENKINS-35184] Servlet API dependent bits in a inner-class

This is in order to avoid loading ServletContextListener class
from slaves classloader.

* [JENKINS-35184] Don't use SystemProperties while initializing remote agents

This rolls back the previous commit and introduces a new way to construct
RingBufferLogHandler which avoids relying on SystemProperties to get the
default size.

* [JENKINS-35184] Mark SystemProperties as OnMaster only class

Adding `OnMaster` annotation does not prevent the class from being
loaded on remote agent but it gives a hint that this class should not
be used on a remote agent.

* [JENKINS-35184] Set SLAVE_LOG_HANDLER at the very beginning

In the previous code cleaning existing log handlers, SLAVE_LOG_HANDLER
is always null, as static fields are scoped by classloader.