This commit introduces a new failure analysis mechanism that can be
used to provide diagnostics to a user when their application fails
to start.

When application context refresh fails. FailureAnalyzer
implementations are loaded via spring.factories. The analyzers are
called in order, with the first non-null analysis of the failure
being used. The analysis is reported to the use by
FailureAnalysisReporters which are also loaded via spring.factories.

A single FailureAnalysisReporter is provided out of the box. It logs
an error message with details of the analysis, providing the user
with a description of the failure and, if available, some actions
that they may be able to take to resolve the problem without also
displaying a stack trace that is of little value.

Two analysers are provided initially. One for an embedded servlet
container port clash and another for BeanCurrentlyInCreationExceptions.
More analysers are planned (for UnsatisfiedDependencyException and for
NoUniqueBeanDefinitionException) once some updates have been made
to Spring Framework to make those failures more amenable to analysis.

Closes gh-4907