Add KDevelop::IRunController::showConfigurationDialog() method

Summary: Old version doesn't provide access to launches configuration page (KDevelop::LaunchConfigurationDialog is an "internal" class), but this functionality is useful for example for run-time analyzers like valgrind or heaptrack plugins for cases when default launch doesn't exists. With new API we can directly show launches configuration page instead message box with text instructions about configuration requirement.

Test Plan: Tested with master branch and valgrind/heaptrack plugins.

Reviewers: KDevelop, mwolff

Reviewed By: KDevelop, mwolff

Subscribers: mwolff, kdevelop-devel

Differential Revision: https://phabricator.kde.org/D4912