Revert "Reland: [DWARF] Allow cross-CU references of subprogram definitions"

... as well as:
Revert "[DWARF] Defer creating declaration DIEs until we prepare call site info"

This reverts commit fa4701e1.

This reverts commit 79daafc9.

There have been reports of this assert getting hit:

CalleeDIE && "Could not find DIE for call site entry origin