Add `Performance impact` tab on live reports page

[lucasmrod]

Goal

User story
As a user running live reports on my hosts,
I want to see performance impact of the query on each host
so that I can determine if the query I'm running is expensive and should be optimized.

Changes

Product

• UI changes:
  • Demo video.
  • PoC branch.
• CLI (fleetctl) usage changes: No changes.
• YAML changes: No changes.
• REST API changes: No changes.
• Fleet's agent (fleetd) changes: No changes.
• Fleet server configuration changes: No changes.
• Exposed, public API endpoint changes: No changes.
• fleetdm.com changes: No changes.
• GitOps mode UI changes: No changes.
• GitOps generation changes: No changes.
• Activity changes: No changes.
• Permissions changes: No changes.
• Changes to paid features or tiers: No changes.
• My device and fleetdm.com/better changes: No changes.
• Usage statistics: No changes.
• Other reference documentation changes: No changes.
• First draft of test plan added
• Once shipped, requester has been notified
• Once shipped, dogfooding issue has been filed

Engineering

• Test plan is finalized
• Contributor API changes: No changes.
• Feature guide changes: No changes.
• Load testing: Yes. Run live reports to many hosts on load test environment.
• This is a premium only feature: No.

Risk assessment

• Requires load testing: Test live reports on the UI with thousands of hosts.
• Risk level: Low

Test plan

• Test running live report on multiple hosts in a way that the Performance impact is different in each host (e.g. file traversal queries), check that the performance impact column for the hosts make sense.
• Test running live report on one host.
• Test live queries with typos (error column).
• Test live queries that return no rows.
• Test live queries that return multiple rows.
• Test live queries on hosts with same hostname (check performance impact column).

UI

• Verify that all UI changes specified in the Figma wireframes are correctly implemented
• Verify expected UI states (loading, empty, error states if applicable)

Confirmation

1. Engineer: Added comment to user story confirming successful completion of test plan (include any special setup, test data, or configuration used during development/testing if applicable).
2. QA: Added comment to user story confirming successful completion of test plan.