release-21.2: opt: fix implicit lateral for SRFs when using JOIN syntax

[blathers-crl]

Backport 1/1 commits from #71396 on behalf of @RaduBerinde.

/cc @cockroachdb/release

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When SRFs are used as a table, they imply that the join is lateral.
This works for the multiple table syntax, but not for the JOIN syntax.
This commit addresses this omission.

Fixes #70342.

Release note (bug fix): Fixes an incorrect "no data source matches
prefix" error for queries that use a set-returning function on the
right-hand side of a JOIN (unless LATERAL is explicitly
specified).

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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.
• 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 

[mgartner]

Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @RaduBerinde and @rytaft)