Add internal assertions to purely fixed-size DenseStorage, mark optional variables always as unused
Add internal assertions to purely fixed-size DenseStorage, mark optional variables always as unused

ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,pasuka/eigen,pasuka/eigen,pasuka/eigen,TSC21/Eigen,ritsu1228/eigen,TSC21/Eigen,TSC21/Eigen,TSC21/Eigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,ritsu1228/eigen,ROCmSoftwarePlatform/hipeigen,pasuka/eigen,pasuka/eigen,ritsu1228/eigen