debugger: rename a few functions

src/plugins/debugger/cdb/cdbdebugengine.cpp

src/plugins/debugger/cdb/cdbdebugengine.h

src/plugins/debugger/debuggermanager.cpp

src/plugins/debugger/debuggermanager.h

src/plugins/debugger/gdb/gdbengine.cpp

src/plugins/debugger/gdb/gdbengine.h

src/plugins/debugger/idebuggerengine.h

src/plugins/debugger/script/scriptengine.cpp

src/plugins/debugger/script/scriptengine.h