Remove std::string alias (for real this time)

Also use std::string_view in a few more places.

src/libstore/remote-store.hh

@@ -83,8 +83,11 @@ public:
         RepairFlag repair,
         CheckSigsFlag checkSigs) override;
 
-    StorePath addTextToStore(const string & name, const string & s,
-        const StorePathSet & references, RepairFlag repair) override;
+    StorePath addTextToStore(
+        std::string_view name,
+        std::string_view s,
+        const StorePathSet & references,
+        RepairFlag repair) override;
 
     void registerDrvOutput(const Realisation & info) override;