[Extractor][DebugInfo] Don't pick DebugLocs from dbg intrinsics (#80863)

When picking the source location for a branch instruction in the
CodeExtractor, we can end up picking the source location of a debugging
intrinsic. This never makes sense because any variable assignment
information (or labels) might originate from completely different
lexical scopes that have been inlined, and also makes the line tables
change between -g and -gmlt. Fix this by skipping debug intrinsics when
looking for branch source locations.

Detected because of test differences with RemoveDIs, the non-intrinsinc
form of debug-info -- fixing in intrinsic form to avoid there being
spurious test differences when we turn it on.