[clang] [clang] Add -Wmissing-designated-field-initializers (PR #81364)

[Shafik Yaghmour via cfe-commits]

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@@ -120,6 +120,10 @@ Non-comprehensive list of changes in this release
 New Compiler Flags
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+- ``-Wmissing-designated-field-initializers``, grouped under ``-Wmissing-designated-field-initializers``.
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shafik wrote:

CC @AaronBallman 

https://github.com/llvm/llvm-project/pull/81364