LPS-46779 Site memberships - Exceptions is thrown when clicks a summary tab after site member is assigned

Hey Brian!

I reviewed what you said in https://github.com/brianchandotcom/liferay-portal/pull/18592.
Three things to mention:

  - We can't use brackets in custom selects because that way, all Hibernate queries must get each row using an entity (`addEntity`), but won't work using scalar (`addScalar`). If you check `countByC_FN_MN_LN_SN_EA_S` method, it uses the same query but with an scalar (`userId`) instead of an entity (`UserImpl`), so `{User_.*}` will break `countBy_Blah_Blah` method.

- We can't use `User_*` without brackets neither because Oracle construction `(SELECT ... UNION SELECT ...) ORDER BY ...` needs explicit column names in order to work. If you get all columns with \*, you cannot sort by those columns. So I added explicitly all columns defined in table `User_`. I'm **not happy** with this solution, because we're adding a weird query in `portal.xml` that nobody will understand. I'd add a comment pointing to [this doc](http://docs.oracle.com/cd/E17952_01/refman-5.1-en/union.html). This way at least devs would understand the decision made. Or even better: I'd write some mechanist in order to have several `custom-sql/model.xml` files (one per DB vendor) and allow devs to define specific *tuned* queries for specific vendor (in this scenario, we'd have `portal.xml` and `portal-oracle.xml`, the former with common queries for all vendors and the latter with overwritten queries). **UPDATE**: check this proposal for custom specific queries: https://github.com/brianchandotcom/liferay-portal/pull/18608

- I reviewed my `SQLQueryImpl` change and you're right: it's not needed, so I reverted it. I thought union queries couldn't use table aliases but it seems they can.

I hope it's clear enough. If not, just ping me!

Thanks!