[num-utils] add SetToUintMax() to prevent type-mismatch bugs (#11969)

Introduces a new template helper function `SetToUintMax()` in
`common/num_utils.hpp`. This function sets a given unsigned integer
variable to its maximum possible value.

The `SetToUintMax()` function infers the type of the variable,
ensuring that the correct `NumericLimits<...>::kMax` is used. This
prevents potential bugs where a variable could be assigned the max
value of a wrong `uint` type.

Existing code across different modules is updated to use this new
helper function, improving code safety and robustness.

src/core/thread/mle_ftd.cpp

@@ -3510,7 +3510,7 @@ Error Mle::AddrSolicitInfo::ParseFrom(const Coap::Message &aMessage)
     case kErrorNone:
         break;
     case kErrorNotFound:
-        mXtalAccuracy = NumericLimits<uint16_t>::kMax;
+        SetToUintMax(mXtalAccuracy);
         break;
     default:
         ExitNow(error = kErrorParse);