Add module_ctx.template Starlark function

[phst]

Description of the feature request:

Create function module_ctx.template with the same interface and semantics as repository_ctx.template.

Which category does this issue belong to?

Rules API

What underlying problem are you trying to solve with this feature?

There's repository_ctx.template to expand a template as part of a repository rule, but no equivalent in module_ctx. This means that module rule implementations that want to expand a template either have to instantiate a private repository rule, or implement template expansion by hand.

Which operating system are you running Bazel on?

macOS

What is the output of bazel info release?

release 8.0.0

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

Didn't find anything on these sites using the search query "module_ctx template"

Any other information, logs, or outputs that you want to share?

Maybe it would be enough to move StarlarkRepositoryContext.createFileFromTemplate into StarlarkBaseExternalContext.

A similar argument could be made for other functions in StarlarkRepositoryContext: delete, rename, patch, symlink.

[phst]

Similar issues: #16144, #22825

[fmeum]

Moving template to StarlarkBaseExternalContext should be all it takes.

An argument in favor of not moving the other methods is that files created by module extensions are temporary in nature and the working directory is deleted after execution. delete, rename, patch and symlink tend to be less useful in that situation and their availability may give a false impression about what module extensions can do. At the same time, they could be occasionally useful.

@meteorcloudy @Wyverald What do you think, should we just go for parity with repository_ctx? template does seem useful for package manager interactions in a module extension.

[comius]

@satyanandak: Repository and module rules (mention of either repository_ctx, module_ctx) are owned by OSS team in their effort to solve problems with external dependencies.

cc @meteorcloudy @Wyverald

[Wyverald]

basically exactly what @fmeum said above. I'm happy to review a PR that adds mctx.template.