[clang] [clang-format] Separate License text and include blocks (PR #77918)

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seranu wrote:

I updated the implementation and tried to include all the feedback I received. Regarding "NewLines between IncludeGroups" I think this is a separate option that, in my opinion, would be best implemented together with "IncludeBlocksStyle::IBS_Regroup" option.

@mydeveloperday I'm not sure if this is what you expected, let me know what you think.

https://github.com/llvm/llvm-project/pull/77918