sql: infrastructure support for hidden columns in views

[knz]

In another commit, we plan to start introducing hidden columns in crdb_internal virtual views. This change is a prerequisite to that.

Release note: None
Informs #93617.

[cockroach-teamcity]

This change is 

[knz]

@mgartner while trying this PR, I discovered the following behavior: SELECT * FROM myview includes hidden columns in the view.

If I use SELECT * FROM mytable (with a table instead of a view), the * does not include hidden columns.

It looks like star expansion for views ignores the Hidden attribute on the column descriptor. Do you know where I should look to fix that?

[knz]

For an example of what I mean in that last comment check out the branch at #93644 and try select * from crdb_internal.ranges (which has been modified to contain hidden columns)

[mgartner]

As far as I can tell, this behavior is correct. The view is created with the columns explicitly listed, and the "hidden-ness" of a column does not propagate to the view. So while the columns are hidden in the table, they are not hidden in the view.

Postgres behaves the same:

marcus=# CREATE TABLE t (a INT);
CREATE TABLE

marcus=# CREATE VIEW v AS SELECT a, tableoid FROM t;
CREATE VIEW

marcus=# SELECT * FROM v;
 a | tableoid
---+----------
(0 rows)

[knz]

ok that works. thanks for checking