Give support to serving mvt-tippecanoe tiles from an url

[doublebyte1]

Overview

This PR fixes a regression bug, introduced by the MVT class refactoring.

Related issue / discussion

#1506

Additional information

The response status codes were fixed, to address the 5 and 6A core requirements from the OGC API - TIles standard.
https://docs.ogc.org/is/20-057/20-057.html

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