[10.x] Fix Accepting nullable Parameters, updated doc block, and null pointer exception handling in batchable trait

[saMahmoudzadeh]

This PR, in batchable trait :

• fix accepting nullable Parameter (withFakeBatch method)
• fix doc block (withFakeBatch method)
• fix null pointer exception (batch method)

Fix Accepting Nullable Parameter in WithFakeBatch method

// before
CarbonImmutable $createdAt = null

// after
?CarbonImmutable $createdAt = null

CarbonImmutable::now()->toImmutable()

Modified the $createdAt assignment to explicitly convert the result of CarbonImmutable::now() to CarbonImmutable using toImmutable(). This guarantees that the type of $createdAt aligns with the expected CarbonImmutable type in the new BatchFake class.

$this->fakeBatch = new BatchFake(
   empty($id) ? (string) Str::uuid() : $id,
   $name,
   $totalJobs,
   $pendingJobs,
   $failedJobs,
   $failedJobIds,
   $options,
   $createdAt ?? CarbonImmutable::now()->toImmutable(),
   $cancelledAt,
   $finishedAt,
);

[saMahmoudzadeh]

I corrected the commit title. It had a spelling mistake.

[saMahmoudzadeh]

Thanks!