[clang-format] Add experimental option to remove LLVM braces

[clang-format] Add experimental option to remove LLVM braces

See the style examples at:
https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

Differential Revision: https://reviews.llvm.org/D116316