[10.x] Adds the firstOrCreate and createOrFirst methods to the HasManyThrough relation

[tonysm]

Added

• Adds the firstOrCreate method to the HasManyThrough relation
• Adds the createOrFirst method to the HasManyThrough relation

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In #48529 we found a bug in the updateOrCreate. The issue was because that method was changed to use the firstOrCreate behind the scenes. Since the firstOrCreate method didn't exist in the relation, the method call was forwarded to the query builder, so the query changed from select users.* from users ... inner join teams ... to select * from users ... inner join teams ..., which resulted in a bug that was causing updates on the wrong model when using updateOrCreate (I shared more context here).

The updateOrCreate was reverted to the previous implementation. However, this bug will still happen if someone calls the ->firstOrCreate() or the ->createOrFirst() methods on a HasManyThrough relation (for the same reason, the method calls would be forwarded to the query builder and it would run a select * from users ... inner join teams ... causing the result to have 2 id columns, which caused the original bug).

We're adding the missing firstOrCreate and createOrFirst methods to fix the issue on the HasManyThrough relation. I was also able to reproduce the original regression error on both methods.