release-24.2: sql/types, sql/stats: fix SQLStringFullyQualified for arrays of UDTs

[michae2]

Backport 1/1 commits from #137448.

/cc @cockroachdb/release

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Starting in v24.2 we added SQLStringFullyQualified, but it looks like it didn't work for arrays of user-defined types. This is only used in a few places, including the output of SHOW STATISTICS USING JSON.

This commit:

1. fixes SQLStringFullyQualified for arrays of UDTs
2. adds the t.TypeMeta.Name == nil guard to SQLString for composite UDTs
3. sets a formatting flag in stats.(*JSONStatistic).SetHistogram so that we get fully-qualified type annotations on histogram upper bounds

No release note because the output of SHOW STATISTICS USING JSON isn't documented.

Fixes: #137443

Release note: None

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Release justification: quality-of-life fix for regression in SHOW STATISTICS which will help with ALTER TABLE INJECT STATISTICS.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
• Backports should change as little code as possible.
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• Backports should not add new functionality (except as defined
  here).
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  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• 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).
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  channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[rytaft]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @dt, @mgartner, and @spilchen)