elf: retrieve all dynamic metadata from the .dynamic table instead of requiring section headers

[alessandrod]

We currently retrieve some tables (eg .dynstr) by name instead of looking up their address in the .dynamic table. This is because some programs have the wrong address encoded in the latter, but otherwise the files as a whole are correct and we're able to load them.

We should review what percentage of programs have this problem and consider rejecting them so we can rely on parsing the .dynamic table only.

OS-ELF-SUG-03