[llvm-readobj/readelf] - Don't fail dumping when unable to read the name of the SHT_DYNSYM section.

We have an issue currently: we are trying to read the name of the SHT_DYNSYM section
very early and using `unwrapOrError` call for that.

The name is needed only for the GNU output. Because of the current logic, the tool
fails to dump the whole object when something is wrong with the name of the .dynsym section.

This patch delays reading the name and also allows it to be broken.

Differential revision: https://reviews.llvm.org/D84173