docs: Add documentation on how to build images

[reubenmiller]

Proposed changes

The following documentation changes are included:

• Yocto build instructions using new meta-tedge-project (using kas)
• Remove existing yocto build instructions (as these are very hard to maintain). In a follow up PR, the meta-rust variant of the image build will be added to the meta-tedge-project once a few technical problems have been resolved.
• Rugpi build instructions
• How to flash an image to an SD Card
• How to onboard a device to Cumulocity (using auto detection via DNS Service Discovery which is built into the images)

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I ran cargo fmt as mentioned in CODING_GUIDELINES
• I used cargo clippy as mentioned in CODING_GUIDELINES
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[didier-wenzek]

This material deserves to be published along 1.0.rc.

[didier-wenzek]

Approved

[github-actions]

Robot Results

✅ Passed	❌ Failed	⏭️ Skipped	Total	Pass %	⏱️ Duration
373	0	3	373	100	57m0.881s