gccrs: Labels shall be pushed within label namespace

gccrs: Labels shall be pushed within label namespace

Labels were using the wrong namespace.

gcc/rust/ChangeLog:

	* resolve/rust-ast-resolve-expr.cc (ResolveExpr::visit): Change label
	push function from type rib to label rib.
	* resolve/rust-ast-resolve-item.cc (ResolveTraitItems::visit):
	Likewise.
	(ResolveItem::visit): Likewise.
	(ResolveExternItem::visit): Likewise.
	* resolve/rust-ast-resolve-stmt.h: Likewise.
	* resolve/rust-ast-resolve.cc (NameResolution::go): Likewise.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>