[clang] [clang-format] Add options to control wrapped lambda brace indent. (PR #143249)

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rmarker wrote:

> See https://clang.llvm.org/docs/ClangFormatStyleOptions.html#adding-additional-style-options. IMO, when it's difficult to name the new options, it will be hard for people to understand what they do. @mydeveloperday WDYT?

I'll have to see if we can get our style guide public. Argh, that will be fun company politics ;)
Trying to first get the style guide to align with clang-format went down in flames.

I think that switching to only including the option for indenting the top level lambdas ((https://github.com/llvm/llvm-project/pull/143249#discussion_r2139472981)) does go a long way to making it a lot more straightforward and clearer to remove any confusion.

In any case, I started work on upgrading to a struct (https://github.com/llvm/llvm-project/pull/143663).
I think keeping support for the previous formatting, with at least a bool for lambda brace indentation is worth it.
Regardless of any small additional nuance that is also possible to include in the option.

https://github.com/llvm/llvm-project/pull/143249