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/basic/object/structured_view.c

@@ -195,7 +195,7 @@ bool Structured_View_Object_Name(
  *
  * @return  true if object-name was set
  */
-bool Structured_View_Name_Set(uint32_t object_instance, char *new_name)
+bool Structured_View_Name_Set(uint32_t object_instance, const char *new_name)
 {
     bool status = false; /* return value */
     struct object_data *pObject;
@@ -234,15 +234,15 @@ const char *Structured_View_Name_ASCII(uint32_t object_instance)
  *
  * @return description text or NULL if not found
  */
-char *Structured_View_Description(uint32_t object_instance)
+const char *Structured_View_Description(uint32_t object_instance)
 {
-    char *name = NULL;
-    struct object_data *pObject;
+    const char *name = NULL;
+    const struct object_data *pObject;
 
     pObject = Keylist_Data(Object_List, object_instance);
     if (pObject) {
         if (pObject->Description) {
-            name = (char *)pObject->Description;
+            name = pObject->Description;
         } else {
             name = "";
         }
@@ -259,7 +259,8 @@ char *Structured_View_Description(uint32_t object_instance)
  *
  * @return  true if object-name was set
  */
-bool Structured_View_Description_Set(uint32_t object_instance, char *new_name)
+bool Structured_View_Description_Set(
+    uint32_t object_instance, const char *new_name)
 {
     bool status = false; /* return value */
     struct object_data *pObject;
@@ -317,15 +318,15 @@ bool Structured_View_Node_Type_Set(
  * @param  object_instance - object-instance number of the object
  * @return Node_Subtype text or NULL if not found
  */
-char *Structured_View_Node_Subtype(uint32_t object_instance)
+const char *Structured_View_Node_Subtype(uint32_t object_instance)
 {
-    char *name = NULL;
-    struct object_data *pObject;
+    const char *name = NULL;
+    const struct object_data *pObject;
 
     pObject = Keylist_Data(Object_List, object_instance);
     if (pObject) {
         if (pObject->Description) {
-            name = (char *)pObject->Node_Subtype;
+            name = pObject->Node_Subtype;
         } else {
             name = "";
         }
@@ -340,7 +341,8 @@ char *Structured_View_Node_Subtype(uint32_t object_instance)
  * @param  new_name - holds the Node_Subtype to be set
  * @return  true if Node_Subtype was set
  */
-bool Structured_View_Node_Subtype_Set(uint32_t object_instance, char *new_name)
+bool Structured_View_Node_Subtype_Set(
+    uint32_t object_instance, const char *new_name)
 {
     bool status = false; /* return value */
     struct object_data *pObject;
@@ -460,7 +462,7 @@ Structured_View_Represents(uint32_t object_instance)
  * @return  true if Represents was set
  */
 bool Structured_View_Represents_Set(
-    uint32_t object_instance, BACNET_DEVICE_OBJECT_REFERENCE *represents)
+    uint32_t object_instance, const BACNET_DEVICE_OBJECT_REFERENCE *represents)
 {
     bool status = false; /* return value */
     struct object_data *pObject;