[wpiutil] Struct: Add info template parameter pack

[PeterJohnson]

This allows using Struct in a dynamically typed environment by passing additional information to the Struct serialization functions.

Fixes #5964.

[PeterJohnson]

/format

[virtuald]

StructPublisher isn't movable because you can't move std::atomic. Looks like your operator= does a store/load thing, the move constructor needs to do the same thing. Here's what I did:

  StructPublisher(StructPublisher&& rhs)
      : Publisher{std::move(rhs)},
        m_info{std::move(rhs.m_info)} {
    m_schemaPublished.store(
        rhs.m_schemaPublished.load(std::memory_order_relaxed),
        std::memory_order_relaxed);
  }

[PeterJohnson]

Fixed.

[virtuald]

LGTM