Combine `tempest/framework` and `tempest/core`

[innocenzi]

[brendt]

Just FYI this is more complex than combining the two. The goal of tempest/core is to be a small base used by standalone packages. If we combine the two, the standalone packages will either include all the framework related stuff as well, or they will need yet another package to depend on.

[aidan-casey]

I honestly cannot see myself reaching for core as a dependency for a package. I'd probably be reaching for one of the other components. Is that just me?

[innocenzi]

@brendt what would you see being kept in tempest/core? Could the packages just depend on whatever Tempest package they rely on?

[brendt]

Maybe things will change now that we're decoupling discovery. Let's see how that goes first and take it from there.