Source Hubspot: schema should load properties dynamically

[eugene-kulak]

Tell us about the problem you're trying to solve

Hubspot entities have dynamic schema, to retrieve a list of available (default and custom) properties we need to call
https://api.hubapi.com/properties/v2/ticket/properties?hapikey=demo (see StreamAPI.properties method).

Describe the solution you’d like

We should have a basic schema in schemas folder for each entity, retrieve properties at run time, merge it with basic and return during discover. Basically, we will reproduce logic in the singer tap (but will make it simpler).
Note: we need this only for entities, i.e. not for streams like contact_lists or data_pipelines

Describe the alternative you’ve considered or used

A clear and concise description of any alternative solutions or features you've considered or are using today.

Additional context

Add any other context or screenshots about the feature request here.

[keu]

implemented as part of #2215