Fix unnecessary required spring-context-support dep

Prior to this commit, a project using compile time weaving upgrading to
4.1 was forced to add spring-context-support and the jcache API in order
to build. This problem is not new really: spring-aspects holds all
aspects provided by the framework and they all are evaluated when
compiling. 4.1 just happens to define a new aspect that requires extra
dependencies.

This commit uses a new annotation of AspectJ 1.8.3. When @RequiredTypes
is added on an aspect, it is evaluated only if the classes defined on the
annotation are actually present. If they are not, the aspect is disabled
and does not break the build.

Issue: SPR-12163