Revert go_googleapis upgrade

[linzhp]

What type of PR is this?
Other

What does this PR do? Why is it needed?
The go_googleapis upgrade in 0.38.0 is too disruptive. It changes the Go import paths of the proto packages like @go_googleapis//google/cloud/dialogflow/cx/v3 and @go_googleapis//google/cloud/dialogflow/v2, making it necessary to change a large number known imports in Gazelle (bazelbuild/bazel-gazelle#1426), which means that people may not be able to upgrade to rules_go 0.38.0 until we release another version of Gazelle.

In addition, it requires other 3rd party packages to use the new import paths too. For example, it requires people to upgrade cloud.google.com/go/dialogflow/apiv2 to at least v1.19.0, which is less than 3 months old, to use the new import path.

We should explore a better upgrade plan, or at least wait a few more months to upgrade go_googleapis. Reverting the upgrade for now.

Other notes for review
I am planning to create a patch release 0.38.1 to include this revert.

[sluongng]

@linzhp @fmeum unfortunately keeping the old version of go_googleapis is blocking folks from using some of the latest dependencies in the ecosystem. This affects the usability of rules_go a lot as some popular libraries such as OpenTelemetry require a new version of these.

Have you guys discussed an upgrade plan? Or do you want to tackle #1986 instead?

[linzhp]

We are planning to see if we can remove the hard-coded import mapping for googleapis and use the pre-generated package managed by Go modules instead. So rules_go and Gazelle no longer need to worry about googleapis.

I am trying to do that for a while, but haven't get there yet. If you have bandwidth, feel free to give it a try.

[sluongng]

I think that's the sane approach.

I can't promise anything but I will be taking a closer look at these code paths to see if I could make a nudge.