Add some Python types to the base provider

[C-Loftus]

Overview

• this PR adds Python types to the base provider
• this makes it so users who are writing custom providers can more clearly understand and validate that their providers are correct
• this should not change any runtime behavior

Related Issue / discussion

N/A

Additional information

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

[C-Loftus]

@webb-ben does this seem like the correct interpretation of the queryables spec? https://docs.ogc.org/is/19-079r2/19-079r2.html#queryables

It appears there are some other properties related to uuid's / uri's but I have never actually seen these in practice. So as such not sure if they should be on the properties type.