Add lifecycle metadata to product/solution and core release manifests

[jtomasek]

Adds additional metadata to solution and core release manifests

• Adds lifecycle section to solution and core release manifests
• In case when lifecycle is defined, at least lifecycle.availabilityDate must be set
• Bumps release manifest schema version to v1, defaults to v0 if not provided
• Removed metadata.creationDate from release manifests, replaced by lifecycle.availabilityDate
• Updated tests
• Updated example manifests
• Updated docs

[jtomasek]

There are a few things I'd like to get feedback on:

We probably want to make the lifecycle section optional and document it's purpose.

The design document also defines lifecycle.stage property. Updating it however requires re-releasing of the specific release manifest image which IIUC is not desirable. We could update the lifecycle.stage property in the codebase without updating the image however I don't think this is something we want to do.

I am quite inclined towards using the Kubernetes Object Model for the release manifest format as it clearly defines

• Type Metadata: (apiVersion and kind) to define the manifest versioning
• Object Metadata: A metadata block for standardized labels and annotations which could be easily utilised for lifecycle properties
• Specification: A spec block containing the corePlatform and components definition.

This approach would also make the product/solution definition close to the EIB based Edge release manifest definition, making the transition more straightforward.