BugFix FlashStringHelper Macros (#8147)

Revert to previous definition of `FPSTR` and `F` macros.

Author: mrengineer7777

cores/esp32/WString.h

@@ -34,8 +34,8 @@
 // A pure abstract class forward used as a means to proide a unique pointer type
 // but really is never defined.
 class __FlashStringHelper;
-#define FPSTR(pstr_pointer) (pstr_pointer)
-#define F(string_literal) (string_literal)
+#define FPSTR(pstr_pointer) (reinterpret_cast<const __FlashStringHelper *>(pstr_pointer))
+#define F(string_literal) (FPSTR(PSTR(string_literal)))
 
 // An inherited class for holding the result of a concatenation.  These
 // result objects are assumed to be writable by subsequent concatenations.