Reapply "[CodeCompletion] Don't show the loop index before it is visible"

With the tests updated to account for not having the correct behaviour
for brace-stmt items from after the code-completion point.  That part
turns out to be harder to fix.

This reverts commit a5325e6281.

lib/Parse/ParseStmt.cpp

@@ -2463,8 +2463,6 @@ ParserResult<Stmt> Parser::parseStmtForEach(SourceLoc ForLoc,
   ParserResult<Expr> Where;
   if (consumeIf(tok::kw_where)) {
     Where = parseExprBasic(diag::expected_foreach_where_expr);
-    if (Where.hasCodeCompletion())
-      return makeParserCodeCompletionResult<Stmt>();
     if (Where.isNull())
       Where = makeParserErrorResult(new (Context) ErrorExpr(Tok.getLoc()));
     Status |= Where;