sql: extend SHOW CREATE TABLE to use fully-qualified names

[yuzefovich]

This commit extends SHOW CREATE TABLE syntax to use fully-qualified names for tables as well as user-defined types used in the table. This is needed to make the recreation of stmt bundles collected on multi-region tables easier. Note that for UDTs this behavior was already the case up until this Summer when we switched to not showing the DB name for portability. The stmt bundle recreation case needs the exact reproduction since we might be dealing with cross-DB references and things like crdb_internal_region type unavailable in the current DB when creating a multi-region table.

SHOW CREATE TABLE syntax is extended to support FULLY_QUALIFIED option. We already had a documented REDACT option, so any combination of these two options is now supported. However, at least as of right now, I chose to not document this new option. We now use the new option when building the stmt bundle.

It is powered by adding two new columns create_statement_fq and create_redactable_fq to crdb_internal.create_statements virtual table. These columns are only populated for tables and will remain empty strings for views and sequences. The delegated show query is adjusted to use the proper column based on the options.

Informs: #99131.
Fixes: #123897.
Epic: None

Release note: None

[cockroach-teamcity]

This change is 

[michae2]

I think it would be a lot simpler to add a USE statement to bundles. If we go down the route of making CREATE statements fully-qualified, wouldn't we have to add that ability to every type of CREATE statement that could appear in schema.sql?

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @spilchen)

[yuzefovich]

We already use some CREATE statements that use fully-qualified names for bundles (and will use more with #137662), and I think we should embrace this approach fully.

I considered using USE statement, but it seemed more error-prone. Consider the following example: we have two MR-enabled databases with a RBR table in each; the schema of RBR table has invisible column of crdb_internal_region type that right now would only have schema in the type name, so we would need to have a sequence like:

CREATE DATABASE mr1 ...;
CREATE DATABASE mr2 ...;
...
USE mr1;
CREATE TABLE t1 ...;
...
USE mr2;
CREATE TABLE t2 ...;

Now let's add user-defined types into the mix. Due to how we populate schema.sql, we would first handle all UDTs, and only then we'd add all tables, so now the file becomes something like:

CREATE DATABASE mr1 ...;
CREATE DATABASE mr2 ...;
...
USE mr1;
CREATE TYPE udt1 ...;
...
USE mr2;
CREATE TYPE udt2 ...;
...
USE mr1;
CREATE TABLE t1 ... <using udt1> ...;
...
USE mr2;
CREATE TABLE t2 ... <using udt2> ...;

Effectively we need to teach the bundle building code to be DB-aware for all objects. I actually started going down this path a bit, but then UDTs needed the special handling in addition to tables, and I thought that adjusting the CREATE stmts themselves would be cleaner (so I added #137580 for UDTs).

The alternative approach (which is what this PR helps with) is to ensure that all CREATE statements included in schema.sql use fully-qualified naming, but we already have that available for some (via crdb_internal.create_*_statements vtables) and it doesn't seem difficult to add that if necessary (see #137580). We use delegated SHOW CREATE statements for tables, sequences, and views that is powered by a more involved query to additionally pull in zone configs, so this PR makes the change to SHOW CREATE TABLE syntax. After this change I think that bundle recreation with cross-db views and sequences still might not work, and we still might need to ensure that fully-qualified naming is used for UDFs and procedures.

---

Having typed this all out, I don't feel strongly about USE approach or this fully-qualified naming in CREATE approach.

[yuzefovich]

I implemented the USE approach in #138023, and it seems cleaner, so let's hold off on this change.

[yuzefovich]

We implemented the USE approach in #138023, so this is no longer needed.