dump: Add architecture section and section string table support

Add hooks which architectures can use to add arbitrary data to custom
sections.

Also add a section name string table in order to identify section
contents

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20221017113210.41674-1-frankja@linux.ibm.com>