[clang-tools-extra] [clang-reorder-fields] Support designated initializers (PR #142150)

[Vladimir Vuksanovic via cfe-commits]

================

----------------
vvuksanovic wrote:

Added `InitializerListExcessElements.c` and `IdiomaticZeroInitializer.c` tests. I can't find test cases for non constant-sized arrays in structs. I would change those checks for asserts, but there might be some way to trigger that, that I didn't think of.

Also modified the message to include the location of the problematic initializer list.

https://github.com/llvm/llvm-project/pull/142150