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>

ports/lwip/bip.c

@@ -67,7 +67,7 @@ uint32_t bip_stats_drop(void)
  * @param addr - network IPv4 address
  * @return true if the address is set
  */
-bool bip_set_addr(BACNET_IP_ADDRESS *addr)
+bool bip_set_addr(const BACNET_IP_ADDRESS *addr)
 {
     return bvlc_address_copy(&BIP_Address, addr);
 }
@@ -87,7 +87,7 @@ bool bip_get_addr(BACNET_IP_ADDRESS *addr)
  * @param network IPv4 broadcast address
  * @return true if the broadcast address is retrieved
  */
-bool bip_set_broadcast_addr(BACNET_IP_ADDRESS *addr)
+bool bip_set_broadcast_addr(const BACNET_IP_ADDRESS *addr)
 {
     return bvlc_address_copy(&BIP_Broadcast_Address, addr);
 }
@@ -137,7 +137,7 @@ uint16_t bip_get_port(void)
  * @param address - IPv4 address from LwIP
  * @param mac - IP address from BACnet/IP
  */
-static void bip_mac_to_addr(ip4_addr_t *address, uint8_t *mac)
+static void bip_mac_to_addr(ip4_addr_t *address, const uint8_t *mac)
 {
     if (mac && address) {
         address->addr = ((u32_t)((((uint32_t)mac[0]) << 24) & 0xff000000));
@@ -153,7 +153,7 @@ static void bip_mac_to_addr(ip4_addr_t *address, uint8_t *mac)
  * @param address - IPv4 address from LwIP
  * @param port - IPv4 UDP port number
  */
-static int bip_decode_bip_address(BACNET_IP_ADDRESS *baddr,
+static int bip_decode_bip_address(const BACNET_IP_ADDRESS *baddr,
     ip_addr_t *address,
     uint16_t *port)
 {
@@ -215,7 +215,7 @@ static int bip_encode_bip_address(BACNET_IP_ADDRESS *baddr,
  * @return number of bytes sent, or 0 on failure.
  */
 int bip_send_mpdu(
-    BACNET_IP_ADDRESS *dest, uint8_t *mtu, uint16_t mtu_len)
+    const BACNET_IP_ADDRESS *dest, const uint8_t *mtu, uint16_t mtu_len)
 {
     struct pbuf *pkt = NULL;
     /* addr and port in host format */