DEFEATURE: remove obsolete optionalData container

- unused and superseded by c++17 std::optional

applications/utilities/preProcessing/PDR/pdrFields/optionalData/optionalData.H

-/*---------------------------------------------------------------------------*\
-  =========                 |
-  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
-   \\    /   O peration     |
-    \\  /    A nd           | www.openfoam.com
-     \\/     M anipulation  |
--------------------------------------------------------------------------------
-    Copyright (C) 2020 OpenCFD Ltd.
--------------------------------------------------------------------------------
-License
-    This file is part of OpenFOAM.
-
-    OpenFOAM is free software: you can redistribute it and/or modify it
-    under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
-    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
-    for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
-
-Class
-    Foam::optionalData
-
-Description
-    A simplified version of std::optional (c++17), with much simpler
-    construction semantics.
-
-\*---------------------------------------------------------------------------*/
-
-#ifndef optionalData_H
-#define optionalData_H
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-namespace Foam
-{
-
-/*---------------------------------------------------------------------------*\
-                        Class optionalData Declaration
-\*---------------------------------------------------------------------------*/
-
-template<class T>
-class optionalData
-{
-    // Private Data
-
-        //- Validity of the value
-        bool good_;
-
-        //- The value
-        T value_;
-
-
-public:
-
-    // Generated Methods
-
-        //- Copy construct
-        optionalData(const optionalData<T>&) = default;
-
-        //- Move construct
-        optionalData(optionalData<T>&&) = default;
-
-        //- Copy assignment
-        optionalData<T>& operator=(const optionalData<T>&) = default;
-
-        //- Move assignment
-        optionalData<T>& operator=(optionalData<T>&&) = default;
-
-
-    // Constructors
-
-        //- Default construct
-        optionalData()
-        :
-            good_(false),
-            value_()
-        {}
-
-        //- Copy construct from value
-        optionalData(const T& val)
-        :
-            good_(true),
-            value_(val)
-        {}
-
-        //- Move construct from value
-        optionalData(T&& val)
-        :
-            good_(true),
-            value_(std::move(val))
-        {}
-
-
-    // Member Functions
-
-        //- True if it has a value
-        bool has_value() const noexcept
-        {
-            return good_;
-        }
-
-        //- Access to the value
-        T& value() noexcept
-        {
-            return value_;
-        }
-
-        //- Access to the value
-        const T& value() const noexcept
-        {
-            return value_;
-        }
-
-        //- Return value or default
-        const T& value_or(const T& deflt) const
-        {
-            return good_ ? value_ : deflt;
-        }
-
-
-    // Member Operators
-
-        //- True if it has a value
-        explicit operator bool() const noexcept
-        {
-            return good_;
-        }
-
-        //- Access the value
-        const T& operator*() const noexcept
-        {
-            return value_;
-        }
-
-        //- Access the value
-        T& operator*() noexcept
-        {
-            return value_;
-        }
-
-        //- Copy assignment from value
-        void operator=(const T& val)
-        {
-            good_ = true;
-            value_ = val;
-        }
-
-        //- Move assignment from value
-        void operator=(T&& val)
-        {
-            good_ = true;
-            value_ = std::move(val);
-        }
-};
-
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-} // End namespace Foam
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-#endif
-
-// ************************************************************************* //