[TASK] Deprecate ConfigurationForm

The call tree of the extension manager "configuration form"
ext_conf_template.txt parser is a mess:
The ext:extensionmanager ConfigurationUtility calls ext:core
ConfigurationForm which is a class that extends ExtendedTemplateService
which extends TemplateService. The "TypoScript" a-like parsing then uses
class TypoScriptParser. This compiles to a huge list of dependencies.

The patch compiles this mess down to a series of methods within
ConfigurationUtility directly, effectively adding needed parts
of TypoScriptParser and ConfigurationForm as protected methods.
The class ends up with way less direct and indirect dependencies.

The various detail parsing methods are still messy and hard to follow,
but rewriting the parser heart does not really make sense since the
ext_conf_template.txt format will bite the dust sooner or later anyway
and having all in one place is already much better than before.
So putting some days of energy into rewriting these specific parts
of the Ty...