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/trendlog.c

@@ -910,7 +910,7 @@ bool TL_Is_Enabled(int iLog)
  * Convert a BACnet time into a local time in seconds since the local epoch  *
  *****************************************************************************/
 
-bacnet_time_t TL_BAC_Time_To_Local(BACNET_DATE_TIME *bdatetime)
+bacnet_time_t TL_BAC_Time_To_Local(const BACNET_DATE_TIME *bdatetime)
 {
     return datetime_seconds_since_epoch(bdatetime);
 }
@@ -1498,7 +1498,7 @@ int TL_encode_entry(uint8_t *apdu, int iLog, int iEntry)
 
 static int local_read_property(uint8_t *value,
     uint8_t *status,
-    BACNET_DEVICE_OBJECT_PROPERTY_REFERENCE *Source,
+    const BACNET_DEVICE_OBJECT_PROPERTY_REFERENCE *Source,
     BACNET_ERROR_CLASS *error_class,
     BACNET_ERROR_CODE *error_code)
 {