Generate proto-plus types for this library

[busunkim96]

This library currently generates _pb2.py types via protoc.

I would like to move this set of protos to be generated via bazel. The repository will look like a full GAPIC library but only have types (no services). If Access Context Manager adds a service in the future the change will be additive (non-breaking). See this repo for an example of the desired end state.

This is a breaking change, but I believe the blast radius will be small - this library is only installed as a dependency of google-cloud-asset (see setup.py).

CC @parthea @danoscarmike

[danoscarmike]

Sounds like the right direction to me.

For clarity, will this be a breaking change for this package only, or will also require a break in Cloud Asset?

A break here only seems fine, but google-cloud-asset is published stable so we should think more about that if necessary.

[busunkim96]

Now that I think about this more some google-cloud-asset will probably be impacted (it depends on how they instantiate the message). Perhaps there's a way to hide the change from end users. 🤔

Will hold on this for now, and address when/if a service is created for Access Context Manager.

[parthea]

@busunkim96 A service appears to be available for the v1 client here. Googlers see b/187964157.

[busunkim96]

👍 let's discuss how to proceed tomorrow.

[parthea]

@busunkim96 Please could you take a look?