Remove deprecated file_provider

[c-parsons]

file_provider has been around for some time, but is almost completely undocumented.

Instead of rushing to document it, we are considering deprecating it as part of the "Fixing Starlark Rule Outputs" document sent to bazel-dev.

This will track following up specifically making a commitment to deprecate or document file_provider.

[jin]

could you add a priority to this issue, please?

[laurentlb]

Any update about the next steps?

[c-parsons]

We've made no additional commitment to remove file_provider as part of the rule outputs cleanup.

Most users shouldn't need to use this provider, and can use DefaultInfo instead. The only place this is used instead of DefaultInfo seems to be in Android rules.