Replace the various `defaults` maps in the schema with per-property
`default` and `defaultInfo` fields. The former holds the static default
value; the latter holds the envvars and language-specific info.
Also, fix a minor bug in the Python codegen that caused diffs in
property docstrings.
The schema format is described in pkg/codegen/schema/schema.go. The code
generators are derived from the code generators contained in
https://github.com/pulumi/pulumi-terraform-bridge/pkg/tfgen, with the
exception of the Go code generator, which is net new.
Fixes: #2151
This will allow us to be able to share the code that generates our
language providers. Currently there is a copy of the python code
generation in pulumi-kubernetes and also in pulumi-terraform
We want to be able to share these
