no ropes WIP (#20433)

* refactorings in preparation for ropes elimination of the C code generator; mostly the usual ': Rope' -> 'result: var Rope' rewrite
* rewrote ccgcalls.nim
* refactored ccgexprs.nim
* ccgliterals: refactoring
* refactoring: code dealing with name mangling
* refactoring: getRecordFieldsAux
* ropes are strings (insert obscene joke here)
* optimize JS code gen
* optimizations and code improvements
* more optimizations
* final cleanups

compiler/semexprs.nim

@@ -2259,7 +2259,7 @@ proc instantiateCreateFlowVarCall(c: PContext; t: PType;
   # codegen would fail:
   if sfCompilerProc in result.flags:
     result.flags.excl {sfCompilerProc, sfExportc, sfImportc}
-    result.loc.r = nil
+    result.loc.r = ""
 
 proc setMs(n: PNode, s: PSym): PNode =
   result = n
@@ -2836,7 +2836,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}, expectedType: PType
     defer:
       if isCompilerDebug():
         echo ("<", c.config$n.info, n, ?.result.typ)
-  
+
   template directLiteral(typeKind: TTypeKind) =
     if result.typ == nil:
       if expectedType != nil and (