x/build: automate consequences of go.mod go directive maintenance

[findleyr]

Recently, we started automating go.mod go directives for x/ repos (#69095).

However, some x/ repos have deployments that target a certain go version, which may be incompatible with the upgraded go.mod file.

Off the top of my head, at least:

• x/telemetry: https://go.dev/cl/656455
• x/pkgsite: https://go.dev/cl/656475
• x/playground
• x/website: https://go.dev/cl/655656

I think the x/ repo automation should include updates to target deployment versions.
Where possible, we should parameterize these deployments, so that this automation doesn't require complicated edits.

CC @dmitshur @jba

[gabyhelp]

Related Issues

• x/pkgsite: set up automated updating of x-repo dependencies #62218 (closed)
• x/build: update x/ dependencies in untagged x/ repos when applying tags #56530 (closed)
• all, x/build/cmd/relui: automate go directive maintenance in golang.org/x repositories #69095 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[dmitshur]

We can add tasks that run after the go directive maintenance happens as part of the major Go release relui workflow, here: https://cs.opensource.google/go/x/build/+/master:internal/relui/workflows.go;l=552-555;drc=b7066079957dd7cad5084b68444c3fc8d30bf63e. (If there's a different timeline that's better for the needs of a given deployment, that's of course fine too.)

To use x/website's golangorg deployment as an example of what can be done, since I'm pretty familiar with it: it's an App Engine app with automatic deploys, so its maintenance CLs are predictable one-line changes like this one and don't need follow up steps as long as the deployment doesn't produce errors.

However, it does require that App Engine has the runtime being switched to; something that's easy to check manually. Not sure if it's worth automating the check; we can instead assume it'll always be there in time.

Some of the smaller App Engine apps also in x/website can also be updated, as done in CLs like this one, but since its deploys are manual, automating only the CL part of it wouldn't be a complete solution.