ENH: new broadcast version of Pstreams (#2371)

- The idea of broadcast streams is to replace multiple master to
  subProcs communications with a single MPI_Bcast.

    if (Pstream::master())
    {
        OPBstream toAll(Pstream::masterNo());
        toAll << data;
    }
    else
    {
        IPBstream fromMaster(Pstream::masterNo());
        fromMaster >> data;
    }

    // vs.
    if (Pstream::master())
    {
        for (const int proci : Pstream::subProcs())
        {
            OPstream os(Pstream::commsTypes::scheduled, proci);
            os << data;
        }
    }
    else
    {
        IPstream is(Pstream::commsTypes::scheduled, Pstream::masterNo());
        is >> data;
    }

  Can simply use UPstream::broadcast() directly for contiguous data
  with known lengths.

Based on ideas from T.Aoyagi(RIST), A.Azami(RIST)

applications/test/parallel-broadcast/Test-parallel-broadcast.C

@@ -0,0 +1,147 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2022 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/>.
+
+Application
+    Test-parallel-broadcast
+
+Description
+    Test for various broadcast routines.
+
+\*---------------------------------------------------------------------------*/
+
+#include "List.H"
+#include "argList.H"
+#include "Time.H"
+#include "vector.H"
+#include "IPstream.H"
+#include "OPstream.H"
+#include "IOstreams.H"
+
+using namespace Foam;
+
+
+// This is what our new scatter will look like inside
+template<class Type>
+void testBroadcastStream
+(
+    Type& value,
+    const label comm = UPstream::worldComm
+)
+{
+    Info<< nl << "is_contiguous:" << is_contiguous<Type>::value << endl;
+    Pout<< "pre-broadcast: " << value << endl;
+
+    if (is_contiguous<Type>::value)
+    {
+         UPstream::broadcast
+         (
+             reinterpret_cast<char*>(&value),
+             sizeof(Type),
+             comm,
+             UPstream::masterNo()
+         );
+    }
+    else
+    {
+        if (UPstream::master())
+        {
+            OPBstream toAll(UPstream::masterNo(), comm);
+            toAll << value;
+        }
+        else
+        {
+            IPBstream fromMaster(UPstream::masterNo(), comm);
+            fromMaster >> value;
+        }
+    }
+
+    Pout<< "post-broadcast: " << value << endl;
+}
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+    argList::noCheckProcessorDirectories();
+    #include "setRootCase.H"
+    #include "createTime.H"
+
+    {
+        label value = -1;
+        if (Pstream::master())
+        {
+            value = UPstream::nProcs();
+        }
+        testBroadcastStream(value);
+    }
+
+    {
+        labelList values;
+        if (Pstream::master())
+        {
+            values = identity(UPstream::nProcs());
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        wordList values;
+        if (Pstream::master())
+        {
+            values.resize(UPstream::nProcs());
+            forAll(values, i)
+            {
+                values[i] = "value_" + Foam::name(i);
+            }
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        vector values(vector::uniform(-1));
+        if (Pstream::master())
+        {
+            values = vector(1,2,3);
+        }
+        testBroadcastStream(values);
+    }
+
+    {
+        FixedList<vector, 3> values(vector::uniform(-1));
+        if (Pstream::master())
+        {
+            values = vector(1,2,3);
+        }
+        testBroadcastStream(values);
+    }
+
+    Info<< "End\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //