[11.x] Improve authenticateViaBearerToken() performance

[alecpl]

One select from oauth_access_tokens and one from oauth_clients less. The issues mentioned in #382.

Before:

select * from `oauth_access_tokens` where `id` = ? limit 1
select * from `oauth_access_tokens` where `id` = ? limit 1
select * from `oauth_clients` where `id` = ? limit 1
select * from `oauth_access_tokens` where `id` = ? limit 1
select * from `oauth_clients` where `id` = ? limit 1

After:

select * from `oauth_access_tokens` where `id` = ? limit 1
select * from `oauth_clients` where `id` = ? limit 1
select * from `oauth_access_tokens` where `id` = ? limit 1

as you see there's still one redundant query, but it might be harder to get rid of it.

[driesvints]

@billriess I think it's best if you go over these changes if you can spare the time?

[billriess]

Is this check still happening somewhere else?

[alecpl]

$this->clients->findActive() above makes sure the $client is not revoked.

[billriess]

I can take a look at this in the next day or two but glancing over it seems good.

[taylorotwell]

I see this was sent to master. Is there a breaking change? Should this go to 10.x?

[alecpl]

@driesvints didn't like the protected method removal.

[driesvints]

@alecpl @taylorotwell technically we could do the changes on 10.x if we left the method in there.

@billriess thanks for reviewing 👍