initcap function expected return type does not match actual

[timsaucer]

Describe the bug

initcap was updated in this PR: #13752

InitcapFunc is reporting that the return type will be Utf8 but if the argument is an Utf8View then the actual returned values are also Utf8View (as I would expect) so we have a difference between the expected and returned types. I think this is a very easy fix.

On part that I could use some help with from someone more experienced with the Utf8View is this: in get_optimal_return_type macro we state that DataType::Utf8View has an optimal return type of of Utf8 during the macro invocation. Is this the best type? Why would we not want to return a Utf8View?

To Reproduce

Call initcap with a Utf8View argument.

Expected behavior

No error. Currently I get this error:

Exception: Arrow error: Invalid argument error: column types must match schema types, expected Utf8 but found Utf8View at column index 0

Additional context

No response