This commit modifies the `DefaultDatabaseClient` implementation in order
to ensure lazier usage of the `Supplier<String>` passed to the sql
method (`DatabaseClient#sql(Supplier)`).
Since technically `DatabaseClient` is an interface that could have 3rd
party implementations, the lazyness expectation is only hinted at in the
`DatabaseClient#sql` javadoc.
Possible caveat: some log statements attempt to reflect the now lazily
resolved SQL string. Similarly, some exceptions can capture the SQL that
caused the issue if known. We expect that these always occur after the
execution of the statement has been attempted (see `ResultFunction`).
At this point the SQL string will be accessible and logs and exceptions
should reflect it as before. Keep an eye out for such strings turning
into `null` after this change, which would indicate the opposite.
Closes gh-29367
d72df5ace4