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/list_element.c

@@ -38,7 +38,7 @@
  * @return Bytes encoded or zero on error.
  */
 int list_element_encode_service_request(
-    uint8_t *apdu, BACNET_LIST_ELEMENT_DATA *list_element)
+    uint8_t *apdu, const BACNET_LIST_ELEMENT_DATA *list_element)
 {
     int len = 0; /* length of each encoding */
     int apdu_len = 0; /* total length of the apdu, return value */
@@ -90,7 +90,7 @@ int list_element_encode_service_request(
  * @return number of bytes encoded, or zero if unable to encode or too large
  */
 size_t list_element_service_request_encode(
-    uint8_t *apdu, size_t apdu_size, BACNET_LIST_ELEMENT_DATA *data)
+    uint8_t *apdu, size_t apdu_size, const BACNET_LIST_ELEMENT_DATA *data)
 {
     size_t apdu_len = 0; /* total length of the apdu, return value */
 
@@ -260,7 +260,7 @@ int list_element_decode_service_request(
  * @return Bytes encoded or zero on error.
  */
 int list_element_error_ack_encode(
-    uint8_t *apdu, BACNET_LIST_ELEMENT_DATA *list_element)
+    uint8_t *apdu, const BACNET_LIST_ELEMENT_DATA *list_element)
 {
     int len = 0; /* length of each encoding */
     int apdu_len = 0; /* total length of the apdu, return value */
@@ -309,7 +309,9 @@ int list_element_error_ack_encode(
  * @return Bytes encoded or zero on error.
  */
 int list_element_error_ack_decode(
-    uint8_t *apdu, uint16_t apdu_size, BACNET_LIST_ELEMENT_DATA *list_element)
+    const uint8_t *apdu,
+    uint16_t apdu_size,
+    BACNET_LIST_ELEMENT_DATA *list_element)
 {
     int len = 0, apdu_len = 0;
     BACNET_ERROR_CLASS error_class = ERROR_CLASS_SERVICES;