Improve docs and enable reliable multi-stage caching

[AaronFriel]

In this PR, we adopt a workaround for Buildkit caching described in these upstream issues:

• Builds with inline caching do not consistently use cache moby/buildkit#3730
• Docker BuildKit caching w/ --cache-from fails every second time, except when using docker-container moby/buildkit#2274
• docker --cache-from with BUILDKIT_INLINE_CACHE does not work every second time moby/buildkit#1981

The workaround is simple: pull images referenced in --cache-from before building.

Accordingly, this PR adds an example to the docs for enabling multi-stage build caching, and addresses related documentation issues:

• Fixes The first line of Image docs are not rendered in the registry. #600
• Fixes Document example for Image to use Buildkit inline caching #592
• Fixes Document that images aren't deleted on destroy #588
• Fixes AWS Private ECR Pull, Build, Push - not pulling in CI #566 (the integration test verifies multi-stage caching using ECR)

Documentation fixes rely on and uses an upstream merged commit for tfgen, following the merge of:

• fix: Enable control of docs by provider authors pulumi-terraform-bridge#1024

[AaronFriel]

@iwahbe It looks like the build fails because the new example references the AWS provider, which isn't installed. I seem to recall there's a PCL binder option to allow it to ignore failures like this, but I don't remember if that works with YAML.

Should I modify generate.go to install the AWS plugin and pin the ECR to a specific version, or what do you think?

[iwahbe]

@iwahbe It looks like the build fails because the new example references the AWS provider, which isn't installed. I seem to recall there's a PCL binder option to allow it to ignore failures like this, but I don't remember if that works with YAML.

Should I modify generate.go to install the AWS plugin and pin the ECR to a specific version, or what do you think?

SkipResourceTypechecking might solve the problem here, but the aws references could be wrong (due to missing global analysis). I would make sure we call pulumi plugin install resource aws vX.Y.Z before we generate any examples. It will both fix the error and ensure we generate the best code we can.

[guineveresaenger]

A few minor changes, but otherwise this is great!

[guineveresaenger]

I think we don't need this block as past! us were smart and we should be already logged in if cacheImages is set - we can use regAuth for the call to pullDockerImage.

[AaronFriel]

Ah, I think as it's written it'll help us implement #497 when we get to it, no harm in keeping the code as it is?

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[github-actions]

Does the PR have any schema changes?

Looking good! No breaking changes found.
No new resources/functions.

[guineveresaenger]

LGTM - thank you!