[LLD][ELF] - Allow relocation sections to appear before their target sections.

It allows handling cases when we have SHT_REL[A] sections before target
sections in objects.

This fixes https://bugs.llvm.org/show_bug.cgi?id=46632

which says: "Normally it is not what compilers would emit. We have to support it,
because some custom tools might want to use this feature, which is not restricted by ELF gABI"

Differential revision: https://reviews.llvm.org/D83469