feat: Update GCP icons (mingrammer#666)

Update existing GCP icons using updated official GCP icons:
see https://cloud.google.com/icons. This includes changes to GCP nodes
and examples shown on the website.

Note, generic icons are updated with the corresponding new generic icon,
except "ai-platform-data-labeling-service.png" since it now has its
own unique icon.

Closes mingrammer#554.

refactor

Author: codeaucafe