[Bazel] Update for 9854f2f3 (Diff library)

Updates the Bazel build for
https://github.com/llvm/llvm-project/commit/9854f2f30f by extracting a
library from llvm-diff. Note that this does not include the new
llvm-livepatch binary, for which the CMake file was added accidentally
and reverted in https://github.com/llvm/llvm-project/commit/fec8f1a008.

Differential Revision: https://reviews.llvm.org/D107586