Normalize CRS handling

[webb-ben]

Overview

• Migrate common CRS functions to pygeoapi/crs.py. Moved code from pygeoapi/api/__init__.py, pygeoapi/api/itemtypes.py, pygeoapi/util.py, and various providers. Much of this code was near duplicate with small differences, making it very hard to track consistent CRS across pygeoapi;
• Add optional always_xy CRS configuration option.
• More reliably extract an integer based SRID from a collection CRS object.
• Normalize handing of storage_crs option in base provider. (To allow a future PR to also subsume mapscript options.projection with the normative configuration vocabulary)

I am holding off from overly mutating the implementation of OACov and OAMap because this branch is already getting to a sizable diff. Very little code was changed, and was mostly just merged from various files into crs.py and test_crs.py. I am working on clarifying CRS handling in pygeoapi as well as documenting the changes within the docs right now.

Related Issue / discussion

Addresses: #2102, #2010

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

[webb-ben]

@justb4 @MTachon @doublebyte1 @tomkralidis any thoughts on this?

[tomkralidis]

I will take a look/review on the weekend.

[tomkralidis]

I will take a look/review on the weekend.

Update: note that I'm still reviewing and will provide feedback in the next day or two (cc @justb4).

[tomkralidis]

@webb-ben can you rebase? Thanks.