release-22.2: sql: fix CREATE TABLE AS sourcing SHOW <show_subcmd> <table> job failures

[blathers-crl]

Backport 1/1 commits from #107099 on behalf of @ecwall.

/cc @cockroachdb/release

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Fixes #106260

Previously CREATE TABLE AS/CREATE MATERIALIZED VIEW AS sourcing from SHOW <show_subcmd> <table> generated a failing schema change job with a relation "tbl" does not exist error because the SHOW source table was not fully qualified.

This PR fixes this by respecting the Builder.qualifyDataSourceNamesInAST flag in delegate.TryDelegate() which implements the failing SHOW commands.

Release note (bug fix): Fix failing schema change job when CREATE TABLE AS or CREATE MATERAILIZED VIEW AS sources from a SHOW command:

1. CREATE TABLE t AS SELECT * FROM [SHOW CREATE TABLE tbl];
2. CREATE TABLE t AS SELECT * FROM [SHOW INDEXES FROM tbl];
3. CREATE TABLE t AS SELECT * FROM [SHOW COLUMNS FROM tbl];
4. CREATE TABLE t AS SELECT * FROM [SHOW CONSTRAINTS FROM tbl];
5. CREATE TABLE t AS SELECT * FROM [SHOW PARTITIONS FROM TABLE tbl];
6. CREATE TABLE t AS SELECT * FROM [SHOW PARTITIONS FROM INDEX tbl@tbl_pkey];

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Release justification:

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[ecwall]

Done in #107227