[llvm-readelf] - Do not error out when dumping symbols.

[llvm-readelf] - Do not error out when dumping symbols.

When the --symbols option/--dyn-symbols is given we might report an
error and exit when something goes not right. E.g. when the SHT_SYMTAB
section is broken. Though we could report a warning and try to continue
dumping instead in many cases.

This patch removes `unwrapOrErr` calls from the code involved in the
flow described.

Differential revision: https://reviews.llvm.org/D82955