Everywhere: Replace single-char StringView op. arguments with chars

This prevents us from needing a sv suffix, and potentially reduces the
need to run generic code for a single character (as contains,
starts_with, ends_with etc. for a char will be just a length and
equality check).

No functional changes.

Userland/Libraries/LibSQL/TupleDescriptor.h

@@ -97,7 +97,7 @@ public:
         for (auto& element : *this) {
             elements.append(element.to_string());
         }
-        return String::formatted("[\n{}\n]", String::join("\n", elements));
+        return String::formatted("[\n{}\n]", String::join('\n', elements));
     }
 
     using Vector<TupleElementDescriptor>::operator==;