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/bactimevalue.h

@@ -79,38 +79,40 @@ extern "C" {
 
     BACNET_STACK_EXPORT
     int bacnet_time_value_encode(uint8_t * apdu,
-        BACNET_TIME_VALUE * value);
+        const BACNET_TIME_VALUE * value);
 
     BACNET_STACK_DEPRECATED("Use bacnet_time_value_encode() instead")
     BACNET_STACK_EXPORT
-    int bacapp_encode_time_value(uint8_t *apdu, BACNET_TIME_VALUE *value);
+    int bacapp_encode_time_value(uint8_t *apdu,
+        const BACNET_TIME_VALUE *value);
 
     BACNET_STACK_EXPORT
     int bacnet_time_value_context_encode(uint8_t * apdu,
         uint8_t tag_number,
-        BACNET_TIME_VALUE * value);
+        const BACNET_TIME_VALUE * value);
 
     BACNET_STACK_DEPRECATED("Use bacnet_time_value_context_encode() instead")
     BACNET_STACK_EXPORT
-    int bacapp_encode_context_time_value(uint8_t *apdu, uint8_t tag_number, BACNET_TIME_VALUE *value);
+    int bacapp_encode_context_time_value(
+        uint8_t *apdu, uint8_t tag_number, const BACNET_TIME_VALUE *value);
 
     BACNET_STACK_DEPRECATED("Use bacnet_time_value_decode() instead")
     BACNET_STACK_EXPORT
-    int bacapp_decode_time_value(uint8_t * apdu,
+    int bacapp_decode_time_value(const uint8_t * apdu,
         BACNET_TIME_VALUE * value);
 
     BACNET_STACK_EXPORT
-    int bacnet_time_value_decode(uint8_t *apdu, int max_apdu_len,
+    int bacnet_time_value_decode(const uint8_t *apdu, int max_apdu_len,
         BACNET_TIME_VALUE *value);
 
     BACNET_STACK_DEPRECATED("Use bacnet_time_value_context_decode() instead")
     BACNET_STACK_EXPORT
-    int bacapp_decode_context_time_value(uint8_t * apdu,
+    int bacapp_decode_context_time_value(const uint8_t * apdu,
         uint8_t tag_number,
         BACNET_TIME_VALUE * value);
 
     BACNET_STACK_EXPORT
-    int bacnet_time_value_context_decode(uint8_t *apdu, int max_apdu_len,
+    int bacnet_time_value_context_decode(const uint8_t *apdu, int max_apdu_len,
         uint8_t tag_number, BACNET_TIME_VALUE *value);
 
     /**
@@ -125,7 +127,7 @@ extern "C" {
      */
     BACNET_STACK_EXPORT
     int bacnet_time_values_context_decode(
-        uint8_t * apdu,
+        const uint8_t * apdu,
         int max_apdu_len,
         uint8_t tag_number,
         BACNET_TIME_VALUE *time_values,
@@ -145,7 +147,7 @@ extern "C" {
     int bacnet_time_values_context_encode(
         uint8_t * apdu,
         uint8_t tag_number,
-        BACNET_TIME_VALUE * time_values,
+        const BACNET_TIME_VALUE * time_values,
         unsigned int max_time_values);
 
 #ifdef __cplusplus