Adding AdiosGlobalComm for global data exchange

[hgangwar]

This PR introduces a Global ADIOS communicator

Key Changes

• Added a new AdiosGlobalComm::Communicator class. This global communicator is intended for exchanging global data and metadata between coupled applications.
• Updated AdiosChannel::CreateComm to route communicator creation through the CommType enum which defines the Ptn and Global communication modes..
• Usage example: This creates a bidirectional communicator associated with the channel.

    auto channel =
        rdv.CreateAdiosChannel(name, params, redev::TransportType::BP4);
    auto commPair =
        channel.CreateComm<redev::Real>(name, comm, redev::CommType::Global);

• The existing API remains unchanged. If CommType is not provided, channel.CreateComm defaults to CommType::Ptn and behaves as before.

• Added a virtual (non-pure) function redev::Communicator::SetCommParams to specify the active variable's name and size.

  • The existing redev::Communicator::send() operated on a raw pointer, which prevented communicating the message size without deducing it from the in/out layout.
  • A single channel using a Global communicator can now read and write multiple variables.

• A testcase to test AdiosGlobalComm.

[cwsmith]

Please explain a bit more in the PR description or ideally, in code comments, what 'global' means and an example of how this is used.

Please also undo all the whitespace changes. It looks like redev_comm.h has many lines of just reformatting.

[jacobmerson]

Let's change this to Partitoned instead of Ptn. It's possible @cwsmith will disagree with me here, but I think it will be more clear to have the full name spelled out what the distinction is between the two options.

Counter argument is we use Ptn for the partition class.

[cwsmith]

Partitioned is fine with me. We just need to be sure the user interface documentation discusses it.

[jacobmerson]

AdiosPartitionedComm

[jacobmerson]

No need to move ctype since it's an enum move will have no impact.

[jacobmerson]

Since we now have the partitioned and global communicators, specify that this communicator works on the partitioned data.