Fixing #7479

Types converted:

- `NixStringContextElem`
- `OutputsSpec`
- `ExtendedOutputsSpec`
- `DerivationOutput`
- `DerivationType`

Existing ones mostly conforming the pattern cleaned up:

- `ContentAddressMethod`
- `ContentAddressWithReferences`

The `DerivationGoal::derivationType` field had a bogus initialization,
now caught, so I made it `std::optional`. I think #8829 can make it
non-optional again because it will ensure we always have the derivation
when we construct a `DerivationGoal`.

See that issue (#7479) for details on the general goal.

`git grep 'Raw::Raw'` indicates the two types I didn't yet convert
`DerivedPath` and `BuiltPath` (and their `Single` variants) . This is
because @roberth and I (can't find issue right now...) plan on reworking
them somewhat, so I didn't want to churn them more just yet.

Co-authored-by: Eelco Dolstra <edolstra@gmail.com>

src/libexpr/primops.cc

@@ -69,7 +69,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
                 res.insert_or_assign(ctxS, ctxS);
                 ensureValid(d.drvPath);
             },
-        }, c.raw());
+        }, c.raw);
     }
 
     if (drvs.empty()) return {};
@@ -1265,7 +1265,7 @@ drvName, Bindings * attrs, Value & v)
             [&](const NixStringContextElem::Opaque & o) {
                 drv.inputSrcs.insert(o.path);
             },
-        }, c.raw());
+        }, c.raw);
     }
 
     /* Do we have all required attributes? */
@@ -1334,13 +1334,13 @@ drvName, Bindings * attrs, Value & v)
             if (isImpure)
                 drv.outputs.insert_or_assign(i,
                     DerivationOutput::Impure {
-                        .method = method.raw,
+                        .method = method,
                         .hashType = ht,
                     });
             else
                 drv.outputs.insert_or_assign(i,
                     DerivationOutput::CAFloating {
-                        .method = method.raw,
+                        .method = method,
                         .hashType = ht,
                     });
         }
@@ -1373,7 +1373,7 @@ drvName, Bindings * attrs, Value & v)
                 drv.env[i] = state.store->printStorePath(outPath);
                 drv.outputs.insert_or_assign(
                     i,
-                    DerivationOutputInputAddressed {
+                    DerivationOutput::InputAddressed {
                         .path = std::move(outPath),
                     });
             }
@@ -1381,7 +1381,7 @@ drvName, Bindings * attrs, Value & v)
             ;
         case DrvHash::Kind::Deferred:
             for (auto & i : outputs) {
-                drv.outputs.insert_or_assign(i, DerivationOutputDeferred {});
+                drv.outputs.insert_or_assign(i, DerivationOutput::Deferred {});
             }
         }
     }
@@ -2054,7 +2054,7 @@ static void prim_toFile(EvalState & state, const PosIdx pos, Value * * args, Val
     StorePathSet refs;
 
     for (auto c : context) {
-        if (auto p = std::get_if<NixStringContextElem::Opaque>(&c))
+        if (auto p = std::get_if<NixStringContextElem::Opaque>(&c.raw))
             refs.insert(p->path);
         else
             state.debugThrowLastTrace(EvalError({