Prepare for lldb plugin: move code from gdb debugger plugin to common one.
Summary:
- New MIDebuggerPlugin, which GDB::CppDebuggerPlugin now inherits from
- Solve old TODOs in GDB::CppDebuggerPlugin
- Move debuggers/gdb/debugjob.* to debuggers/common/midebugjobs.*
- New MIExamineCoreJob and MIAttachProcessJob
- Move process selection dialog and select core dialog to common
Test Plan: unit tests under gdb folder
Reviewers: apol, KDevelop
Reviewed By: apol, KDevelop
Subscribers: kdevelop-devel
Differential Revision: https://phabricator.kde.org/D1975