gdb: remove move constructor and move assignment operator from cooked_index

gdb: remove move constructor and move assignment operator from cooked_index

Building with clang++-14, I see:

      CXX    dwarf2/cooked-index.o
    In file included from /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.c:21:
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.h:172:12: error: explicitly defaulted move constructor is implicitly deleted [-Werror,-Wdefaulted-function-deleted]
      explicit cooked_index (cooked_index &&other) = default;
               ^
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.h:225:16: note: move constructor of 'cooked_index' is implicitly deleted because field 'm_storage' has a deleted move constructor
      auto_obstack m_storage;
                   ^
    /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/gdb_obstack.h:128:28: note: 'auto_obstack' has been explicitly marked deleted here
      DISABLE_COPY_AND_ASSIGN (auto_obstack);
                               ^
    In file included from /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.c:21:
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.h:174:17: error: explicitly defaulted move assignment operator is implicitly deleted [-Werror,-Wdefaulted-function-deleted]
      cooked_index &operator= (cooked_index &&other) = default;
                    ^
    /home/smarchi/src/binutils-gdb/gdb/dwarf2/cooked-index.h:225:16: note: move assignment operator of 'cooked_index' is implicitly deleted because field 'm_storage' has a deleted move assignment operator
      auto_obstack m_storage;
                   ^
    /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/gdb_obstack.h:128:3: note: 'operator=' has been explicitly marked deleted here
      DISABLE_COPY_AND_ASSIGN (auto_obstack);
      ^
    /home/smarchi/src/binutils-gdb/gdb/../include/ansidecl.h:425:8: note: expanded from macro 'DISABLE_COPY_AND_ASSIGN'
      void operator= (const TYPE &) = delete
           ^

We explicitly make cooked_index have a default move constructor and
move assignment operator.  But it doesn't actually happen because
cooked_index has a field of type auto_obstack, which isn't movable.
We don't actually need cooked_index to be movable at the moment, so
remove those lines.

Change-Id: Ifc1fe3d7d67e3ae1a14363d6c1869936fe80b0a2