[DebugInfo] Fix methods of AsmPrinter to emit values corresponding to the DWARF format (1/19).

These methods are used to emit values which are 32-bit in DWARF32 and
64-bit in DWARF64. The patch fixes them so that they choose the length
automatically, depending on the DWARF format set in the Context.

Differential Revision: https://reviews.llvm.org/D87008