[SYCL] Fixed-size groups and partitions are renamed to "chunks"

[AndreiZibrov]

Part 1: fix for #15721 review

[AlexeySachkov]

Strictly speaking, there should be no unrelated formatting changes, but in this particular case it is more of a nitpicking and can be ignored.

[AndreiZibrov]

the formatting task failed until I called clang-format -i per changed file

upd:
not-strictly:

cd ../llvm &&
git diff --cached --name-only --diff-filter=ACM | grep '\.[ch]pp$'|xargs -I{} clang-format -i```

[AndreiZibrov]

Topic will be resolved with next commit.

The clang-format tool could be used for essential code as Alexei Sachkov has shared

Previously used way is patching only the changed files but not the file regions

export PATH="$(pwd)/build/bin:$PATH"
git diff -U0 --no-color --relative HEAD^ | $(find -name clang-format-diff.py) -p1 -i

[AlexeySachkov]

As @steffenlarsen said in the original #15721, we should change all non-uniform groups at about the same time, so let's keep this one as a draft until other PRs for other non-uniform groups are ready