chore(tests): Change liveness check for eventually_conservation

[blt]

Summary

The previous version of eventually_conservation relied on polling /metrics to infer
whether or not the data topology in the scenarios were active. This inference is a
race, metrics/ might report while the source/sink are still coming online, so in a
small number of cases scenarios failed on this race. The approach taken here is to
bump the "is it back online" check to 180s and poll directly on the topology, not
on /metrics. I've taken the opportunity to slim vector_e2e a little further also,
removing vestigial restart config update material.

This rare failure will be fixed in the disk buffer scenario as well.

Vector configuration

How did you test this PR?

Antithesis scenario run cycle.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Notes

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[blt]

• Expand vector-buffers property model to include crashes, writebacks #25639
• chore(tests): Change liveness check for eventually_conservation #25667 👈 (View in Graphite)
• master

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[datadog-vectordotdev]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

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