[12.x] Add whereIf() method to Eloquent Builder

[flpdev]

This PR introduces the whereIf() method in Illuminate\Database\Eloquent\Builder.

🔹 Purpose:

The whereIf() method allows conditionally applying a where() clause based on a boolean condition.
This improves readability and eliminates the need for using when() for simple conditional filters.

🔹 Usage:

// If condition is true, it applies the where clause
User::whereIf(true, 'status', '=', 'active')->get(); 
// Equivalent to ->where('status', '=', 'active')

// If condition is false, it does NOT apply the where clause
User::whereIf(false, 'status', '=', 'active')->get(); 
// Equivalent to User::query()->get() (no additional filter)

[shaedrich]

There have already been two tries via #53303 (whenWhere()) and #54312 (whenGrouped()) this year to implement such functionality, so I doubt, this one has better chances

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!