Add utils to support demo datasource project

[tinahollygb]

Adds some utils to support approach discussed in this tech spec with @lukesonnet.

[linear]

GB-290 Demo Datasource -> Create shared util functions

• Create a util getDemoDatasourceProjectIdForOrganization(id: string): string which constructs a demo project ID e.g. prj_org-abc123_demo-datasource-project. This will prevent additional round trips to Mongo for verifying that we can create resources under this project (so we don’t have to query projects by ID with isDemo=true. (add to shared package)
• Create a util isDemoDatasourceProject(organizationId, projectId). (add to shared package)

[github-actions]

Your preview environment pr-1477-bttf has been deployed.

Preview environment endpoints are available at:

• https://growthbook-3000-pr-1477-bttf.growthbook.okteto.dev
• https://growthbook-3100-pr-1477-bttf.growthbook.okteto.dev