...in favor of existing new-style configuration::theDefaultProvider singleton.

Theoretically, ConfigurationProvider instances can be created with specific
Locale and EnableAsync arguments, but this is hardly used in practice, and thus
effectively all uses of the ConfigurationProvider service use the
theDefaultProvider instance, anyway.

theDefaultProvider is restricted to the XMultiServiceFactory interface, while
ConfigurationProvider also makes available XComponent.  However, dispose must
not be called manually on theDefaultProvider singleton anyway, and calls to
add-/removeEventListener are so few (and in dubious code that should better be
cleaned up) that requiring an explicit queryInterface does not really hurt
there.

This commit originated as a patch by Noel Grandin to "Adapt
configuration::ConfigurationProvider UNO service to new style [by creating] a
merged XConfigurationProvider interface for this service to implement."  It was
then modified by Stephan Bergmann by deprecating ConfigurationProvider instead
of adding XConfigurationProvider and by replacing calls to
ConfigurationProvider::create with calls to theDefaultProvider::get.

Change-Id: I9c16700afe0faff1ef6f20338a66bd7a9af990bd