The ``setup.py`` had ALWAUS contained provider dependencies,
but this is really a remnant of Airlfow 1.10 where providers
were not separated out to subfolders of "providers".

This change moves all the provider-specific dependencies
to provider.yaml where they are kept together with all other
provider meta-data.

Later, when we move providers out, we can move them to
provider specific setup.py files (or let provider-specific
setup.py files read them from provider.yaml) but this is
not something we want to do it now.

The dependencies.json is now renamed to provider_dependencies.json
and moved to "airflow" so tha it can be kept as part of the
sources needed for sdist package to provide extras. Pre-commit still
generates the file as needed and it contains now both:

* cross-provider-deps information which providers depend on each
  other
* deps - information what regular dependencies are needed for each
  provider

On top of preparing to splitting providers it has the advantage,
that there will be no more case where adding a dependency change
for provider will not run tests for that provider.