Polywrap project manifest schema refactor

[pileks]

Partially closes #1057

This PR performs the 1st steps of the refactor of the Polywrap project manifest files (wasm, interface, plugin, app).

Things to note:

• The loading of polywrap.app.yaml, polywrap.plugin.yaml etc. have been left as such for backwards compatibility.
  • [x] We might want to consider a CLI command to migrate the YAML files to the latest format version, instead of just reading them and migrating them upwards. Opening an issue seems like a good idea - any thoughts/concerns?
  • [x] Create an issue for a polywrap manifest CLI command, with option for migrating the manifest to the latest version
• [x] It has been decided to use major.minor.patch versioning (as per semver) instead of just major.minor for now - this allows us to circumvent the yaml parser from reading format: 0.2 as a number and forcing us to use format: “0.2”
• [x] Important: All manifest files within the project have been left on version 0.1 for the time being in order to keep builds working with the existing polywrap CLI pulled from npm. I advise we leave them as such until we publish a version of the CLI wich supports the 0.2.0 project manifest format.
  • [x] Explicitly test migrations
  • [x] Move test manifests to 0.2.0