Add 'activity log' to each project

[nlhkabu]

We want to be able to expose information on the changes that have been made to a project over time.
In particular, this will be useful for viewing which maintainer uploaded different files.

From a UI perspective, this could either be added as an extra tab on the project sidebar, or exposed via a toggle button on the changelog panel.

The data to expose is located here: https://github.com/pypa/warehouse/blob/master/warehouse/packaging/models.py#L420-L461

As part of this issue, we may want to add some more structure to the data collected.

[dstufft]

Adding structure to this data will probably depend on when it actually gets done. If legacy is shut down then adding structure becomes a lot easier to do than trying to do it prior to that.

[nlhkabu]

From my POV this is fine to wait for until after legacy is shut down, so lets go with that :)

[nlhkabu]

I think this is a duplicate of #2871