Add a `@MockBean` annotation which can be used to setup and inject mocks
into an application context. The annotation can be used on test classes,
test fields, configuration classes or configuration fields. When used on
a field the annotation also acts as an injection point.
Fixes gh-5042
Add AnsiPropertySource which allows named ANSI codes to be resolved
and update ResourceBanner to include it.
This commit also deprecates constants defined in AnsiElement and
replaces them with AnsiStyle, AnsiColor and AnsiBackground enums.
Closes gh-2704