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/timesync.c

@@ -27,8 +27,8 @@
  */
 int timesync_encode_apdu_service(uint8_t *apdu,
     BACNET_UNCONFIRMED_SERVICE service,
-    BACNET_DATE *my_date,
-    BACNET_TIME *my_time)
+    const BACNET_DATE *my_date,
+    const BACNET_TIME *my_time)
 {
     int len = 0; /* length of each encoding */
     int apdu_len = 0; /* total length of the apdu, return value */
@@ -55,7 +55,7 @@ int timesync_encode_apdu_service(uint8_t *apdu,
  * @return Count of encoded bytes.
  */
 int timesync_utc_encode_apdu(
-    uint8_t *apdu, BACNET_DATE *my_date, BACNET_TIME *my_time)
+    uint8_t *apdu, const BACNET_DATE *my_date, const BACNET_TIME *my_time)
 {
     return timesync_encode_apdu_service(
         apdu, SERVICE_UNCONFIRMED_UTC_TIME_SYNCHRONIZATION, my_date, my_time);
@@ -70,7 +70,7 @@ int timesync_utc_encode_apdu(
  * @return Count of encoded bytes.
  */
 int timesync_encode_apdu(
-    uint8_t *apdu, BACNET_DATE *my_date, BACNET_TIME *my_time)
+    uint8_t *apdu, const BACNET_DATE *my_date, const BACNET_TIME *my_time)
 {
     return timesync_encode_apdu_service(
         apdu, SERVICE_UNCONFIRMED_TIME_SYNCHRONIZATION, my_date, my_time);
@@ -86,7 +86,7 @@ int timesync_encode_apdu(
  *
  * @return Count of decoded bytes.
  */
-int timesync_decode_service_request(uint8_t *apdu,
+int timesync_decode_service_request(const uint8_t *apdu,
     unsigned apdu_len,
     BACNET_DATE *my_date,
     BACNET_TIME *my_time)
@@ -240,7 +240,7 @@ int timesync_encode_timesync_recipients(
  *   BACNET_STATUS_ABORT if there was a problem decoding the buffer
  */
 int timesync_decode_timesync_recipients(
-    uint8_t *apdu, unsigned max_apdu, BACNET_RECIPIENT_LIST *recipient)
+    const uint8_t *apdu, unsigned max_apdu, BACNET_RECIPIENT_LIST *recipient)
 {
     int len = 0;
     int apdu_len = 0;