[branch-54] Expand scalar async UDF results to the batch row count (#25828) - #27372

## Which issue does this PR close?

- Closes apache#25875

## Rationale for this change

When an async UDF returns a `ColumnarValue::Scalar` (e.g. all arguments
are literals), queries on more than one row fail with `all columns in a
record batch must have the same length`.

## What changes are included in this PR?

`AsyncFuncExpr::invoke_with_args` expands each result to its chunk's row
count via `into_array_of_size`, instead of turning a scalar into a 1-row
array.

## What is the testing strategy for this PR?

Added `test_async_udf_with_scalar_result` in
`user_defined_async_scalar_functions.rs`. It fails without the fix.

## Are there any user-facing changes?

No.

(cherry picked from commit 1aed7dc)