chore: e2e-test top shards table

[astandrik]

Closes #2073

CI Results

Test Status: ✅ PASSED

📊 Full Report

Total	Passed	Failed	Flaky	Skipped
298	298	0	0	0

Test Changes Summary ✨6

✨ New Tests (6)

1. TopShards tab defaults to Immediate mode (tenant/diagnostics/diagnostics.test.ts)
2. TopShards immediate tab shows all expected column headers (tenant/diagnostics/diagnostics.test.ts)
3. TopShards history tab shows all expected column headers (tenant/diagnostics/diagnostics.test.ts)
4. TopShards tab first row has values for all columns in Immediate mode (tenant/diagnostics/diagnostics.test.ts)
5. TopShards tab first row has values for all columns in History mode (tenant/diagnostics/diagnostics.test.ts)
6. TopShards tab can switch back to Immediate mode from Historical mode (tenant/diagnostics/diagnostics.test.ts)

Bundle Size: ✅

Current: 83.25 MB | Main: 83.25 MB
Diff: 0.00 KB (0.00%)

✅ Bundle size unchanged.

ℹ️ CI Information

• Test recordings for failed tests are available in the full report.
• Bundle size is measured for the entire 'dist' directory.
• 📊 indicates links to detailed reports.
• 🔺 indicates increase, 🔽 decrease, and ✅ no change in bundle size.

[Copilot]

Pull Request Overview

This PR introduces e2e tests for the TopShards table in diagnostics and updates the memory viewer widget to improve verification and numeric formatting.

• Added a mock data generator for TopShards table in History mode.
• Extended diagnostics tests to cover Immediate and Historical modes for TopShards.
• Updated memory viewer tests to handle decimal values in GB formatting.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/suites/tenant/diagnostics/mocks.ts	Adds a mock data generator for simulating TopShards table rows
tests/suites/tenant/diagnostics/diagnostics.test.ts	Introduces new tests covering mode selection and header validations
tests/suites/tenant/diagnostics/Diagnostics.ts	Adds methods for header verification and TopShards mode selection
tests/suites/memoryViewer/memoryViewer.test.ts	Updates regex in memory tests to support decimals in GB values