[Object] Add zstd decompression support to Decompressor

llvm::object::Decompressor is used by many DWARF consumers like llvm-dwarfdump,
llvm-dwp, llvm-symbolizer. Add tests to them. The lldb test can be left to
D133530.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D134116