[10.x] Revert from using createOrFirst in other *OrCreate methods

[tonysm]

Changed

• After the addition of createOrFirst, other *OrCreate methods were updated to use it behind the scenes. It turns out this was more problematic than we initially thought. This PR reverts using createOrFirst in other methods, but we'll keep it around for the specific scenario it was designed for: using unique constraints to determine if it should create or find the record.

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I've tested the test case added in #48529 and it passes when we revert these changes here.

There was a comment here mentioning an issue, which might be related (it was also on updateOrCreate). We didn't have a way to reproduce the issue.

Reverted PRs:

• [10.x] Enhancing updateOrCreate() to Use firstOrCreate() #48160
• [10.x] Make the firstOrCreate methods in relations use createOrFirst behind the scenes #48192
• And one change of the original PR where I added the createOrFirst to the firstOrCreate in the builder alone: [10.x] Adds a createOrFirst method to Eloquent #47973

[tonysm]

I went ahead to dig a bit more into what was going on over here and found a few things:

1. The firstOrCreate method is missing on the HasManyThrough, which was causing the query call to be forwarded to the Eloquent Query Builder
2. The HasManyThrough::firstOrNew differs from the one from other places. Nothing serious, but it doesn't match, so it may cause some other issues (it was already like that before the introduction of the createOrFirst method)

1. The firstOrCreate method is missing on HasManyThrough

The firstOrCreate method is missing in the HasManyThrough, so when the updateOrCreate method was calling it, the call was forwarded to the Eloquent Builder, which was the root cause. When I added the firstOrCreate method definition there, the issue was fixed.

The queries it was forming when forwarding to the query builder:

select * from "users" inner join "teams" on "teams"."id" = "users"."team_id" where "teams"."owner_id" = 3 and ("name" = "John") limit 1

update "users" set "slug" = "john-doe" where "id" = 1

The queries it was forming when I added the firstOrCreate definition to the HasManyThrough method:

select "users".*, "teams"."owner_id" as "laravel_through_key" from "users" inner join "teams" on "teams"."id" = "users"."team_id" where "teams"."owner_id" = 3 and ("name" = "John") limit 1

update "users" set "slug" = "john-doe" where "id" = 2

We can see that because it was forwarding the call to the base query builder, it was doing a select *, and when that's combined with the inner join, we were getting two IDs back, the one from the teams table and the one from the users table.

Adding the firstOrCreate method definition to the HasManyThrough fixes the issue because it does a select users.*, teams.owner_id instead of a select *.

2. The HasManyThrough::firstOrNew signature is different than in other places

I noticed that the HasManyThrough::firstOrNew method signature differs from the ones in other places. This doesn't seem to have anything to do with the issue, but it may cause other issues (I'm surprised it's like that):

grep -Rn " firstOrNew" src   
src/Illuminate/Database/Eloquent/Builder.php:552:    public function firstOrNew(array $attributes = [], array $values = [])
src/Illuminate/Database/Eloquent/Relations/HasOneOrMany.php:218:    public function firstOrNew(array $attributes = [], array $values = [])
src/Illuminate/Database/Eloquent/Relations/BelongsToMany.php:603:    public function firstOrNew(array $attributes = [], array $values = [])
src/Illuminate/Database/Eloquent/Relations/HasManyThrough.php:257:    public function firstOrNew(array $attributes)

As you can see, it only takes the unique attributes and doesn't even accept the values.

• The HasManyThrough::firstOrNew definition
• The HasOneOrMany::firstOrNew definition for comparison.

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I suggest that we do:

1. Add the firstOrCreate as well as the createOrFirst (this one is also missing) methods to the HasManyThrough relation class to avoid other issues if someone tries to use them and it gets forwarded to the base query builder instead
2. Fix the firstOrNew method signature & implementation in the HasManyThrough

[tonysm]

I've implemented the suggestions in #48541 and #48542.