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/timestamp.c

@@ -34,7 +34,7 @@ void bacapp_timestamp_sequence_set(BACNET_TIMESTAMP *dest, uint16_t sequenceNum)
  * @param dest  Pointer to the destination time stamp structure.
  * @param btime  Pointer to the BACNet time structure.
  */
-void bacapp_timestamp_time_set(BACNET_TIMESTAMP *dest, BACNET_TIME *btime)
+void bacapp_timestamp_time_set(BACNET_TIMESTAMP *dest, const BACNET_TIME *btime)
 {
     if (dest && btime) {
         dest->tag = TIME_STAMP_TIME;
@@ -49,7 +49,7 @@ void bacapp_timestamp_time_set(BACNET_TIMESTAMP *dest, BACNET_TIME *btime)
  * @param bdateTime  Pointer to the BACNet date/time structure.
  */
 void bacapp_timestamp_datetime_set(
-    BACNET_TIMESTAMP *dest, BACNET_DATE_TIME *bdateTime)
+    BACNET_TIMESTAMP *dest, const BACNET_DATE_TIME *bdateTime)
 {
     if (dest && bdateTime) {
         dest->tag = TIME_STAMP_DATETIME;
@@ -62,7 +62,7 @@ void bacapp_timestamp_datetime_set(
  * @param dest  Pointer to the destination time stamp structure.
  * @param src   Pointer to the source time stamp structure.
  */
-void bacapp_timestamp_copy(BACNET_TIMESTAMP *dest, BACNET_TIMESTAMP *src)
+void bacapp_timestamp_copy(BACNET_TIMESTAMP *dest, const BACNET_TIMESTAMP *src)
 {
     if (dest && src) {
         dest->tag = src->tag;
@@ -88,7 +88,8 @@ void bacapp_timestamp_copy(BACNET_TIMESTAMP *dest, BACNET_TIMESTAMP *src)
  * @param value2 - complex data value 2 structure
  * @return true if the two complex data values are the same
  */
-bool bacapp_timestamp_same(BACNET_TIMESTAMP *value1, BACNET_TIMESTAMP *value2)
+bool bacapp_timestamp_same(
+    const BACNET_TIMESTAMP *value1, const BACNET_TIMESTAMP *value2)
 {
     bool status = false;
 
@@ -137,7 +138,7 @@ bool bacapp_timestamp_same(BACNET_TIMESTAMP *value1, BACNET_TIMESTAMP *value2)
  *
  * @return Bytes encoded or 0 on error.
  */
-int bacapp_encode_timestamp(uint8_t *apdu, BACNET_TIMESTAMP *value)
+int bacapp_encode_timestamp(uint8_t *apdu, const BACNET_TIMESTAMP *value)
 {
     int len = 0; /* length of each encoding */
 
@@ -178,7 +179,7 @@ int bacapp_encode_timestamp(uint8_t *apdu, BACNET_TIMESTAMP *value)
  * @return Bytes encoded or 0 on error.
  */
 int bacapp_encode_context_timestamp(
-    uint8_t *apdu, uint8_t tag_number, BACNET_TIMESTAMP *value)
+    uint8_t *apdu, uint8_t tag_number, const BACNET_TIMESTAMP *value)
 {
     int len = 0; /* length of each encoding */
     int apdu_len = 0;
@@ -216,7 +217,7 @@ int bacapp_encode_context_timestamp(
  * @return number of bytes decoded, or BACNET_STATUS_ERROR if an error occurs
  */
 int bacnet_timestamp_decode(
-    uint8_t *apdu, uint32_t apdu_size, BACNET_TIMESTAMP *value)
+    const uint8_t *apdu, uint32_t apdu_size, BACNET_TIMESTAMP *value)
 {
     int len = 0;
     int apdu_len = 0;
@@ -289,7 +290,7 @@ int bacnet_timestamp_decode(
  * @return number of bytes decoded, or BACNET_STATUS_ERROR if an error occurs
  * @deprecated use bacnet_timestamp_decode() instead
  */
-int bacapp_decode_timestamp(uint8_t *apdu, BACNET_TIMESTAMP *value)
+int bacapp_decode_timestamp(const uint8_t *apdu, BACNET_TIMESTAMP *value)
 {
     return bacnet_timestamp_decode(apdu, MAX_APDU, value);
 }
@@ -304,7 +305,7 @@ int bacapp_decode_timestamp(uint8_t *apdu, BACNET_TIMESTAMP *value)
  *               take the time stamp values.
  * @return number of bytes decoded, or BACNET_STATUS_ERROR if an error occurs
  */
-int bacnet_timestamp_context_decode(uint8_t *apdu,
+int bacnet_timestamp_context_decode(const uint8_t *apdu,
     uint32_t apdu_size,
     uint8_t tag_number,
     BACNET_TIMESTAMP *value)
@@ -342,7 +343,7 @@ int bacnet_timestamp_context_decode(uint8_t *apdu,
  * @deprecated use bacnet_timestamp_context_decode() instead
  */
 int bacapp_decode_context_timestamp(
-    uint8_t *apdu, uint8_t tag_number, BACNET_TIMESTAMP *value)
+    const uint8_t *apdu, uint8_t tag_number, BACNET_TIMESTAMP *value)
 {
     const uint32_t apdu_size = MAX_APDU;
     int len;
@@ -442,7 +443,7 @@ bool bacapp_timestamp_init_ascii(BACNET_TIMESTAMP *timestamp, const char *ascii)
  * @return number of characters printed
 */
 int bacapp_timestamp_to_ascii(char *str, size_t str_size,
-    BACNET_TIMESTAMP *timestamp)
+    const BACNET_TIMESTAMP *timestamp)
 {
     int str_len = 0;