Fix value label ranges resolution (#1572)

There was a bug how value labels were resolved, which caused some DWARF expressions not be transformed, e.g. those are in the registers.

*    Implements FIXME in expression.rs
*    Move TargetIsa from CompiledExpression structure
*    Fix expression format for GDB
*    Add tests for parsing
*    Proper logic in ValueLabelRangesBuilder::process_label
*    Tests for ValueLabelRangesBuilder
*    Refactor build_with_locals to return Iterator instead of Vec<_>
*    Misc comments and magical numbers

crates/debug/src/transform/utils.rs

@@ -134,19 +134,17 @@ pub(crate) fn append_vmctx_info(
     isa: &dyn TargetIsa,
 ) -> Result<(), Error> {
     let loc = {
-        let endian = gimli::RunTimeEndian::Little;
-
-        let expr = CompiledExpression::vmctx(isa);
-        let mut locs = Vec::new();
-        for (begin, length, data) in
-            expr.build_with_locals(scope_ranges, addr_tr, frame_info, endian)?
-        {
-            locs.push(write::Location::StartLength {
-                begin,
-                length,
-                data,
-            });
-        }
+        let expr = CompiledExpression::vmctx();
+        let locs = expr
+            .build_with_locals(scope_ranges, addr_tr, frame_info, isa)
+            .map(|i| {
+                i.map(|(begin, length, data)| write::Location::StartLength {
+                    begin,
+                    length,
+                    data,
+                })
+            })
+            .collect::<Result<Vec<_>, _>>()?;
         let list_id = comp_unit.locations.add(write::LocationList(locs));
         write::AttributeValue::LocationListRef(list_id)
     };