refactor(rome_cli): improve the stability of the `max_diagnostics` tests

[leops]

Summary

The tests for the --max-diagnostics CLI arguments are failing semi-randomly (it seems to happen mostly with macOS on CI but I managed to reproduce the failure at least once on Windows), this PR tries to improve these tests by counting the console messages emitted for diagnostics but still checking the rest of the console output against a snapshot to try and narrow down the issue

Test Plan

Run the new tests on CI

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[ematipico]

@leops any chance to get this merged and see if we're able to lower the random failures?

[leops]

@leops any chance to get this merged and see if we're able to lower the random failures?

Yes we could try to merge it, I'll rebase it and move it out of draft

[calibre-analytics[bot]]

Comparing refactor(rome_cli): improve the stability of the max_diagnostics tests Snapshot #1 to median since last deploy of rome.tools.

	LCP?	CLS?	TBT?
Overall Median across all pages and test profiles	465ms  from 274ms	0.049  from 0.009	0ms no change
Chrome Desktop Chrome Desktop • Cable	465ms  from 274ms	0.013  from 0.005	88ms  from 19ms
iPhone, 4G LTE iPhone 12 • 4G LTE	241ms  from 238ms	0.082  from 0.009	0ms no change
Motorola Moto G Power, 3G connection Motorola Moto G Power • Regular 3G	1.2s  from 1.07s	0.049  from 0.009	0ms no change

1 page tested

 Home

Browser previews

Chrome Desktop	iPhone, 4G LTE	Motorola Moto G Power, 3G connection

Most significant changes

	Value	Budget
Total JavaScript Size in Bytes Chrome Desktop	1.33 MB  from 86.8 KB
Total JavaScript Size in Bytes iPhone, 4G LTE	1.33 MB  from 86.8 KB
Total JavaScript Size in Bytes Motorola Moto G Power, 3G connection	1.33 MB  from 86.8 KB
Cumulative Layout Shift iPhone, 4G LTE	0.082  from 0.009
Cumulative Layout Shift Motorola Moto G Power, 3G connection	0.049  from 0.009

_{17 other significant changes: Number of Requests on Chrome Desktop, Number of Requests on iPhone, 4G LTE, Number of Requests on Motorola Moto G Power, 3G connection, Total Blocking Time on Chrome Desktop, Total Page Size in Bytes on Chrome Desktop, Total Page Size in Bytes on iPhone, 4G LTE, Total Page Size in Bytes on Motorola Moto G Power, 3G connection, JS Parse & Compile on Chrome Desktop, Total Image Size in Bytes on Chrome Desktop, Total Image Size in Bytes on iPhone, 4G LTE, Total Image Size in Bytes on Motorola Moto G Power, 3G connection, Total CSS Size in Bytes on Chrome Desktop, Total CSS Size in Bytes on iPhone, 4G LTE, Total CSS Size in Bytes on Motorola Moto G Power, 3G connection, Total HTML Size in Bytes on Chrome Desktop, Total HTML Size in Bytes on iPhone, 4G LTE, Total HTML Size in Bytes on Motorola Moto G Power, 3G connection}

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