fix(native): Watchdog fails to run on certain setups (#26255)

## Description
After a recent change #25855, the
Watchdog fails to run if the hardware_concurrency() returns an odd
number.
The root cause is that `0.5 * hardwareConcurrency()` fails to cast to a
`size_t`

## Motivation and Context
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<!---If it fixes an open issue, please link to the issue here.-->

## Impact
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performance impact-->

## Test Plan
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```
== NO RELEASE NOTE ==
```

Author: majetideepak

presto-native-execution/presto_cpp/main/common/Configs.cpp

@@ -166,7 +166,7 @@ SystemConfig::SystemConfig() {
           NUM_PROP(kDriverStuckOperatorThresholdMs, 30 * 60 * 1000),
           NUM_PROP(
               kDriverCancelTasksWithStuckOperatorsThresholdMs, 40 * 60 * 1000),
-          NUM_PROP(kDriverNumStuckOperatorsToDetachWorker, 0.5 * hardwareConcurrency()),
+          NUM_PROP(kDriverNumStuckOperatorsToDetachWorker, std::round(0.5 * hardwareConcurrency())),
           NUM_PROP(kSpillerNumCpuThreadsHwMultiplier, 1.0),
           STR_PROP(kSpillerFileCreateConfig, ""),
           STR_PROP(kSpillerDirectoryCreateConfig, ""),