* Add initial wording for system topology term of art.
* Add initial proposal for `system_topology`
* Add initial proposal for `this_system::discover_topology`.

* Introduce terms of art for system resource and topology discovery
policy.
* Introduce minimal `system_resource` class.
* Introduce free function `traverse_topology` for traversing a
`system_topology` according to a topology traversal policy.
* Update the changelog.

* Remove `timestamp` member function until we can decide on the
granularity of `discover_topology`.
* Update link to P0443 to point to latest revision.
* Change return value of `traverse_topology` to a
ranges::view<system_resource>`.

* Make the return type of `traverse_topology` be to be defined and add
note about potential options.
* Add more detail to open questions section.