Improve objdump's handling of compressed sections.

Improve objdump's handling of compressed sections.

  PR 31062
  * objdump.c (decompressed_dumps): New local variable. (usage): Mention the -z/--decompress option. (long_options): Add --decompress. (dump_section_header): Add "COMPRESSED" to the Flags field of any compressed section. (dump_section): Warn users when dumping a compressed section. (display_any_bfd): Decompress the section if decompressed_dumps is true. (main): Handle the -z/--decompress option.
  * NEWS: Mention the new feature.
  * doc/binutils.texi: Document the new feature.
  * testsuite/binutils-all/objdump.s: Update expected output.
  * testsuite/binutils-all/objdump.exp: Add test of -Z -s.
  * testsuite/binutils-all/objdump.Zs: New file.
  * readelf.c (maybe_expand_or_relocate_section): New function. Contains common code found in dump functions.  Adds a note message if a compressed section is not being decompressed. (dump_section_as_strings): Use new function. (dump_section_as_bytes): Likewise.