Allow the Batch and Chain onQueue method to accept Backed Enums

[onlime]

Continuing the journey of better enums support in L11 ...

This PR improves the PendingChain and PendingBatch's onQueue method to accept Backed Enums directly as the queue parameter.

Before:

Bus::chain($jobs)
    ->onQueue(QueueName::long->value)->dispatch();

With this PR, you can now pass the Backed Enum directly:

Bus::chain($jobs)
    ->onQueue(QueueName::long)->dispatch();

[zakariaarrid]

@onlime what about UnitEnum ?
@param \UnitEnum|\BackedEnum|string|null $queue

[onlime]

@onlime what about UnitEnum ? @param \UnitEnum|\BackedEnum|string|null $queue

Hi @zakariaarrid I guess it's "too early" to support this now, as all the previous PRs were just about BackedEnum and there must be some reason for it (but don't ask me, I am just following Laravel's current practices...):

• [11.x] Allow the authorize method to accept Backed Enums directly #53330
• [11.x] Update Authorizable methods with BackedEnum support #53079
• [11.x] Add Illuminate\Support\enum_value to resolve BackedEnum or UnitEnum to scalar #53096
• [11.x] Allows Unit & Backed Enums for registering named RateLimiter & RateLimited middleware #52935

The enum_value() helper supports both BackedEnum and UnitEnum, so honestly I don't see any reason against adding \UnitEnum to all docblocks. But for consistency, this should be done in all the other spots as well.

So maybe someone can comment about this backed mystery.