Previously, a number of Actuator endpoints ignored a context hierarchy
or assumed that it would always be linear. This commit reworks the
affected endpoints so that the no longer assume a linear hierarchy.

A side-effect of a non-linear hierarchy is that there may be multiple
different beans with the same name (in a linear hierarchy, a bean
with the same name as one in an ancestor context, replaces that bean).
The affected endpoints have also been updated so that, when bean names
are used as keys, those keys are grouped by application context. This
prevents a bean in one context from accidentially overwriting a bean
in another context.

Closes gh-11019