Add setting clippy_output_diagnostics to match rustc_output_[...]

[refi64]

Right now, capturing clippy's diagnostics is in a weird place. capture_clippy_output exists, but it has drastically different behavior from rustc_output_diagnostics in that it captures the rendered error output and hides it from the terminal, whereas rustc_output_diagnostics captures the raw JSON and still prints out the rendered diagnostics.

The loss of the JSON is a bit of an issue. With that, the only way to get JSON output from the command-line is to set clippy_error_format, which will necessarily clear the analysis cache and rebuild all the targets, meaning that you can't get both rendered output and JSON output without either rebuilds in-between or relying on custom transitions.

This adds the missing equivalent to rustc_output_diagnostics in the form of a new option, clippy_output_diagnostics. In an ideal world, I'd imagine this would be the only option to capture clippy output (since for most intents and purposes, it's strictly a superset of capture_clippy_output), but using a separate option and output group preserves backwards compatibility while retaining the parallel naming of rustc_output_diagnostics vs clippy_output_diagnostics, as well as the output groups rustc_output vs clippy_output.

[refi64]

(00:34:55) ERROR: /workdir/docs/BUILD.bazel:259:8: in deps attribute of starlark_doc_extract rule //:rust_settings.extract: missing bzl_library targets for Starlark module(s) @bazel_skylib//lib:structs.bzl. Since this rule was created by the macro 'stardoc', the error might have been caused by the macro implementation
(00:34:55) ERROR: /workdir/docs/BUILD.bazel:259:8: Analysis of target '//:rust_settings.extract' failed
(00:34:55) ERROR: Analysis of target '//:publish_book' failed; build aborted: Analysis failed

I seem to be constantly finding new ways to fail CI. (should be fixed now.)

[illicitonion]

Makes sense to me - thanks!