Update doxygen and fix documentation (#5106)

Update Doxyfile to version 1.9.1

Re-enable doxygen CI checker

Fix some regular comments that should have been doc comments

Document void return types for some inline functions explicitly

Move start of some doxygen groups so they are included always, and not left
out of certain ifdefs

Ignore some doxygen warnings:
    Member (function) is not documented in headers
    Documented empty return type in headers
    Argument has multiple @param documentation sections

JerryScript-DCO-1.0-Signed-off-by: Máté Tokodi mate.tokodi@szteszoftver.hu

jerry-core/ecma/base/ecma-helpers-errol.c

@@ -78,6 +78,8 @@ typedef struct
 
 /**
  * Normalize the number by factoring in the error.
+ *
+ * @return void
  */
 static inline void JERRY_ATTR_ALWAYS_INLINE
 ecma_normalize_high_prec_data (ecma_high_prec_t *hp_data_p) /**< [in, out] float pair */
@@ -90,6 +92,8 @@ ecma_normalize_high_prec_data (ecma_high_prec_t *hp_data_p) /**< [in, out] float
 
 /**
  * Multiply the high-precision number by ten.
+ *
+ * @return void
  */
 static inline void JERRY_ATTR_ALWAYS_INLINE
 ecma_multiply_high_prec_by_10 (ecma_high_prec_t *hp_data_p) /**< [in, out] high-precision number */