Add any_value aggregate function

[Kevin-Li-2025]

Which issue does this PR close?

• Closes Add any_value aggregate function #22799.

Rationale for this change

any_value is a common aggregate in SQL engines for queries that need one representative non-null value from each group without imposing an ordering requirement. DataFusion currently has first_value, but that aggregate is order-sensitive, so exposing any_value gives users the intended arbitrary-value semantics directly.

What changes are included in this PR?

• Adds an any_value(expression) aggregate UDF and registers it with the default aggregate functions.
• Reuses the existing trivial first-value accumulator with nulls ignored, so evaluation short-circuits after the first non-null value.
• Marks the aggregate as order-insensitive and preserves the input field metadata/type in the return field.
• Adds sqllogictest coverage for scalar, grouped, all-null, empty-input, and string return-type cases.

Are these changes tested?

Yes. I ran:

cargo fmt --all
cargo test -p datafusion-functions-aggregate
cargo test -p datafusion-sqllogictest --test sqllogictests -- aggregate_any_value.slt
cargo clippy --all-targets --all-features -- -D warnings

Are there any user-facing changes?

Yes. This adds a new SQL aggregate function, any_value.

I used AI assistance to help inspect the codebase and run validation, and I reviewed the resulting implementation and tests.

[Jefffrey]

fyi @haohuaijin

[Jefffrey]

are these two tests technically deterministic?

[Jefffrey]

maybe lets add a test for all nulls column