[clang] [-Wunsafe-buffer-usage] Support span creation from std::initializer_list and begin/end pairs (PR #145311)

[Hans Wennborg via cfe-commits]

zmodem wrote:

As a side effect (by changing DataInvocationGadget), this seems to have made -Wunsafe-buffer-usafe warn on unsafe uses of `std::string::data()`. (https://crbug.com/428945428).

Was that intentional, and if so is there some test that should be updated to "lock it in"?

https://github.com/llvm/llvm-project/pull/145311