Record element type of first element in LazyDynaList.transform

[rootvector2]

transform never records the element type for the first non-null element, so the homogeneity check at the end of the method is dead code and mismatched types are silently accepted (add(new HashMap<>()) then add("a POJO String") is accepted), and toArray()/toDynaBeanArray() throw NullPointerException from Array.newInstance(elementType, size()) because elementType stays null; found while auditing the lazy dyna utilities, fixed by recording the type from the first populated element, mirroring setElementDynaClass, which also restores the documented Map[] round-trip in Example 1.

• Read the contribution guidelines for this project.
• Read the ASF Generative Tooling Guidance if you use Artificial Intelligence (AI).
• I used AI to create any part of, or all of, this pull request. Which AI tool was used to create this pull request, and to what extent did it contribute?
• Run a successful build using the default Maven goal with mvn; that's mvn on the command line by itself.
• Write unit tests that match behavioral changes, where the tests fail if the changes to the runtime are not applied. This may not always be possible, but it is a best practice.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Each commit in the pull request should have a meaningful subject line and body. Note that a maintainer may squash commits during the merge process.