Source sweep: Use cmStrCat for string concatenation

This patch is generated by a python script that uses regular expressions to
search for string concatenation patterns of the kind

```
std::string str = <ARG0>;
str += <ARG1>;
str += <ARG2>;
...
```

and replaces them with a single `cmStrCat` call

```
std::string str = cmStrCat(<ARG0>, <ARG1>, <ARG2>, ...);
```

If any `<ARGX>` is itself a concatenated string of the kind

```
a + b + c + ...;
```

then `<ARGX>` is split into multiple arguments for the `cmStrCat` call.

If there's a sequence of literals in the `<ARGX>`, then all literals in the
sequence are concatenated and merged into a single literal argument for
the `cmStrCat` call.

Single character strings are converted to single char arguments for
the `cmStrCat` call.

`std::to_string(...)` wrappings are removed from `cmStrCat` arguments,
because it supports numeric types as well as string types.

`arg.substr(x)` arguments to `cmStrCat` are replaced with
`cm::string_view(arg).substr(x)`

Source/cmFileAPI.cxx

@@ -407,9 +407,7 @@ const char* cmFileAPI::ObjectKindName(ObjectKind kind)
 
 std::string cmFileAPI::ObjectName(Object const& o)
 {
-  std::string name = ObjectKindName(o.Kind);
-  name += "-v";
-  name += std::to_string(o.Version);
+  std::string name = cmStrCat(ObjectKindName(o.Kind), "-v", o.Version);
   return name;
 }