GCP Cloud Functions example

[AymenSegni]

Link related issues:

• Resolves Cover all basic resources for GCP #49: Serverless / FaaS

Changes/added features:

• Create GCP Cloud Functions and deploy a simple hello world app on it
  The following short checklist should be used to make sure your PR is of good quality, and can be merged easily:
• follows project conventions
• follows project principles
• ./run.sh works correctly for all new examples
• CI checks pass
• mergeable to main (no conflicts)
• resolved issues linked
• Milestone linked (if applicable)

[Ileriayo]

• fixed an issue with incorrect source path using path.module and referenced the doc
• also saw that we needed to add some permission in order to be able to trigger the function as an unauthenticated user on the internet to see the hello world message
  cc: @AymenSegni @frankscholten @mo-abdallaa