Reland "[lldb/Fuzzer] Add fuzzer for expression evaluator"

This reverts commit d959324e.

The target_include_directories in the clang-fuzzer CMake files
are set to PRIVATE instead of PUBLIC to prevent the clang buildbots
from breaking when symlinking clang into llvm.

The expression evaluator fuzzer itself has been modified to prevent a
bug that occurs when running it without a target.