align OACov to latest specification updates

[tomkralidis]

Overview

This PR aligns OACov support to latest specification updates. Specifically:

• removes the /collections/{collectionId}/coverage/domainset endpoint in lieu of enhanced metadata at /collections/{collectionId}
• removes the /collections/{collectionId}/coverage/rangetype endpoint in lieu of OAFeat Part 5 /collections/{collectionId}/schema (supported for features/records as well)

Related issue / discussion

None

Additional information

None

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
• https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[tomkralidis]

PR ready for review (needs squash and merge thereafter).