Migrate GCP dashboards from Metric to Samples

[jlegoff]

Summary

This PR converts all GCP dashboards from Metric to Samples. This is because the GCP integrations send samples natively and this data will not be converted to dimensional metrics.

Pre merge checklist

• Did you check you NRQL syntax? - Does it work?
• Did you include a Data source and Documentation reference?
• Are all documentation links publicly accessible?
• Did you check your descriptive content for voice and tone?
• Did you check your descriptive content for spelling and grammar errors?
• Did you review your content with a subject matter expert? (e.g. a Browser agent quickstart is reviewed with a member of the Browser Agent team)

Dashboards

• Does the PR contain a screenshot for each of your dashboards?
• Do your screenshots show data?
• Has the sanitization script been run on each dashboard?

Alerts

• Did you check that your alerts actually work?

[mdumpati]

LGTM