Add Multi Cloud terraform example

[felix-lessoer]

This PR will add a new terraform example. The example is installing an complete multi cloud monitoring environment.

Description

New example that installs Elastic Cloud + all necessary cloud components and much more.

Motivation and Context

It shows more diverse usage example for the terraform provider.

How Has This Been Tested?

It has been tested locally - as it is only an example I would not recommend it for production usage. It's meant to help customers start quick and easy.

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (improves code quality but has no user-facing effect)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• New example

Readiness Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed