Add a grand total event counter to the status output

[6yozo]

Add a grand total event counter to the status output

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

Review this pull request file-by-file.

[dominiklohmann]

Some minor remarks:

• The first two commits in this look unrelated to me.
• There's an integration test that needs an adjustment.
• Right now there's an ambiguity if there's a schema named total, which I think we can avoid by putting the sum in the outer statistics object.

[tobim]

I think we should emit this info for vast status without --detailed too.