feat(dashboards): Add span-first support for web vital dashboard

[Lms24]

Adds support for the new browser.web_vital.<vital>.value attributes to the web vital pre built dashboard queries. This ensures the pre-built dashboard is compatible with streamed v2 web vital spans and attributes.
I left the hard-coded score attributes as-is, since these seem to be handled correctly already.

Reviewers, please let me know if you want to tackle this differently or are already working on it. I mainly oriented myself on #113046 but happy to change anything or close the PR!

My naive assumption was that through coalescing we can switch to querying the new attributes and it works for the old ones as well. Tested with projects sending transactions as well as projects sending v2 spans and both still seem to work.

[github-actions]

📊 Type Coverage Diff

Metric	Before	After	Delta
Coverage	93.56%	93.56%	±0%
Typed	135,666	135,670	🟢 +4
Untyped	9,336	9,334	🟢 -2

🔍 2 new type safety issues introduced

Non-null assertions (!) (2 new)

File	Line	Detail
static/app/views/insights/browser/webVitals/components/performanceScoreRingWithTooltips.tsx	90	projectData?.[0]?.[p75(${SpanFields.BROWSER_WEB_VITAL_CLS_VALUE})]!
static/app/views/insights/browser/webVitals/components/performanceScoreRingWithTooltips.tsx	93	projectData?.[0]?.[p75(${WEB_VITAL_TO_FIELD[webVital]})]!

This is informational only and does not block the PR.