Make most of functions const correct (#714)

* Make most of the functions const correct

Used clang-tidy and sonarlint to help find places where const could
pretty easily applied. Also lot of hand work.

This commit does not yet touch handlers and typedefs of those.

* Fix Arduino uno handler_who_is() has extra parenthesis

For some reason there is extra parenthesis. Remove it this is more
likely buildable.

* Bugfix/bacapp: Fix uninitilized array_index

We have changed bacapp_snprintf_value() to be const correct. After that
we got

```
/home/runner/work/bacnet-stack/bacnet-stack/src/bacnet/bacapp.c:3183:27: warning: 4th function call argument is an uninitialized value [core.CallAndMessage]
                ret_val = bacapp_snprintf_weeklyschedule(
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
```

So analyzer could now spot that we do not actually initilize array_index
at all. Fix this by setting array_index to zero. Note that I actually do
not know if zeroing is right thing to do here. I choose zero as if this
has worked before it is most likely that it will work with zero value.

* cmake: Add and ignore Wwrite-strings compiler option

Wwrite-strings helps find places where const correctness is broken.

Example it will warn about these

```C

void func1(char* str);

func("test") /* "test" is const so we should not pass it to func1().

char* func2()
{
  return "test"; /* func2() should return const char*.
}
```

We still need to ignore it as not all are fixed but let's add it already
so we remember that it should be opened at some point.

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

src/bacnet/calendar_entry.c

@@ -27,7 +27,7 @@
  * @param value Pointer to the property data to be encoded.
  * @return bytes encoded or zero on error.
  */
-int bacnet_calendar_entry_encode(uint8_t *apdu, BACNET_CALENDAR_ENTRY *value)
+int bacnet_calendar_entry_encode(uint8_t *apdu, const BACNET_CALENDAR_ENTRY *value)
 {
     int len = 0;
     int apdu_len = 0;
@@ -68,7 +68,7 @@ int bacnet_calendar_entry_encode(uint8_t *apdu, BACNET_CALENDAR_ENTRY *value)
  * @return  number of bytes encoded, or 0 if unable to encode.
  */
 int bacnet_calendar_entry_context_encode(
-    uint8_t *apdu, uint8_t tag_number, BACNET_CALENDAR_ENTRY *value)
+    uint8_t *apdu, uint8_t tag_number, const BACNET_CALENDAR_ENTRY *value)
 {
     int len = 0;
     int apdu_len = 0;
@@ -99,7 +99,7 @@ int bacnet_calendar_entry_context_encode(
  * @return number of bytes decoded, or BACNET_STATUS_REJECT
  */
 int bacnet_calendar_entry_decode(
-    uint8_t *apdu, uint32_t apdu_size, BACNET_CALENDAR_ENTRY *entry)
+    const uint8_t *apdu, uint32_t apdu_size, BACNET_CALENDAR_ENTRY *entry)
 {
     int apdu_len = 0;
     int len = 0;
@@ -174,7 +174,7 @@ int bacnet_calendar_entry_decode(
  *
  * @return number of bytes decoded, or BACNET_STATUS_REJECT
  */
-int bacnet_calendar_entry_context_decode(uint8_t *apdu,
+int bacnet_calendar_entry_context_decode(const uint8_t *apdu,
     uint32_t apdu_size,
     uint8_t tag_number,
     BACNET_CALENDAR_ENTRY *value)
@@ -211,7 +211,7 @@ int bacnet_calendar_entry_context_decode(uint8_t *apdu,
  * @param month - month to compare
  * @return true if the same month including special values, else false
  */
-static bool month_match(BACNET_DATE *date, uint8_t month)
+static bool month_match(const BACNET_DATE *date, uint8_t month)
 {
     if (month == 0xff) {
         return true;
@@ -231,7 +231,7 @@ static bool month_match(BACNET_DATE *date, uint8_t month)
  * @param weekofmonth - week of the month to compare
  * @return true if the same week of the month including special values
  */
-static bool weekofmonth_match(BACNET_DATE *date, uint8_t weekofmonth)
+static bool weekofmonth_match(const BACNET_DATE *date, uint8_t weekofmonth)
 {
     bool st = false;
     uint8_t day_to_end_month;
@@ -272,7 +272,7 @@ static bool weekofmonth_match(BACNET_DATE *date, uint8_t weekofmonth)
  * @param dayofweek - day of the week to compare
  * @return true if the same day of the week including special values
  */
-static bool dayofweek_match(BACNET_DATE *date, uint8_t dayofweek)
+static bool dayofweek_match(const BACNET_DATE *date, uint8_t dayofweek)
 {
     if (dayofweek == 0xff) {
         return true;
@@ -291,7 +291,7 @@ static bool dayofweek_match(BACNET_DATE *date, uint8_t dayofweek)
  * @return true if a BACnetCalendarEntry includes the BACnetDate value
  */
 bool bacapp_date_in_calendar_entry(
-    BACNET_DATE *date, BACNET_CALENDAR_ENTRY *entry)
+    const BACNET_DATE *date, const BACNET_CALENDAR_ENTRY *entry)
 {
     if (!entry) {
         return false;
@@ -332,7 +332,7 @@ bool bacapp_date_in_calendar_entry(
  * @return true if both BACnetCalendarEntry are the same
  */
 bool bacnet_calendar_entry_same(
-    BACNET_CALENDAR_ENTRY *value1, BACNET_CALENDAR_ENTRY *value2)
+    const BACNET_CALENDAR_ENTRY *value1, const BACNET_CALENDAR_ENTRY *value2)
 {
     if (!value1 || !value2) {
         return false;