Add resource container selector resolver

[mpkorstanje]

Overview

Resolve resource container selectors

As a follow up for #3630 and #3705 this adds a
addResourceContainerSelectorResolver()
method to EngineDiscoveryRequestResolver.Builder analogous to
addClassContainerSelectorResolver().

Points of note:

• As classpath resources can be selected from packages, the package
  filter should also be applied. To make this possible the base path of
  a resource is rewritten to a package name prior to being filtered.

• The ClasspathResourceSelector now has a getClasspathResource
  method. This method will lazily try to load the resource if not was
  not already provided when discovering resources in a container.

• selectClasspathResource(Resource) was added to short circuit the
  need to resolve resources twice. And to make it possible to use
  this method as part of the public API,
  ReflectionSupport.tryToLoadResource was also added.

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes