[llvm-dwp] Add SHF_COMPRESSED support and remove .zdebug support

clang 14 removed -gz=zlib-gnu and ld.lld/llvm-objcopy removed .zdebug support
recently. llvm-dwp currently doesn't support SHF_COMPRESSED. Add support and
remove .zdebug support.

Simplify llvm::object::Decompressor which has no .zdebug user now.

While here, add tests for ELF32LE, ELF32BE, and ELF64BE.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D129728