[REQUEST]: Rename "Elastic instance" to "Elastic Cloud resource"

[shainaraskas]

Description

renaming the generic "instances" umbrella term for ECH deployments + serverless projects to "Elastic Cloud resources"

excludes instances that comprise a deployment

todo:

• update narrative docs in docs-content Replace "Instance" with "Elastic Cloud resource" #1136
• check cloud tooling docs in cloud (done: no instances found)
• check API docs

Resources

see https://github.com/elastic/cloud/issues/139405

Which documentation set does this change impact?

Elastic Cloud (Hosted and Serverless) only

What release is this request related to?

N/A

Collaboration model

The documentation team

Point of contact.

Main contact: @alxchalkias