[llvm] [Github][CI] Add `doc8` for clang-tidy documentation formatting (PR #168827)

[Baranov Victor via llvm-commits]

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@@ -94,6 +94,10 @@ COPY --from=llvm-downloader /llvm-extract/LLVM-${LLVM_VERSION}-Linux-X64/bin/cla
 COPY clang-tools-extra/clang-tidy/tool/clang-tidy-diff.py ${LLVM_SYSROOT}/bin/clang-tidy-diff.py
 
 # Install dependencies for 'pr-code-lint.yml' job
+RUN apt-get update && \
+    DEBIAN_FRONTEND=noninteractive apt-get install -y python3-doc8 && \
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vbvictor wrote:

Could you measure how much bigger code-lint container becomes with this change. If it become reasonably bigger, we can probably install doc8 with `requirements_linting`.

Note that on average 100mb of container size brings ~1sec more in each job run because of longer downloading. So keeping size small get us benefits in long run.

https://github.com/llvm/llvm-project/pull/168827