Which issue does this PR close?

• Part of EPIC: complete GroupValuesColumn type coverage (nested types + remaining primitives) #22715.

Rationale for this change

multi_group_by::group_column_supported_type gates which GROUP BY columns may
use the column-wise GroupValuesColumn fast path, and the gate is
all-or-nothing: a single unsupported column forces the entire grouping onto
the byte-encoded GroupValuesRows fallback, even when every other key column
would have qualified. A Duration key triggers exactly that today, so an
otherwise-qualifying multi-column GROUP BY pays the row-encoding tax because of
one column.

Duration shares the i64 native representation already used by Timestamp,
so supporting it is a pure slot-in of the existing PrimitiveGroupValueBuilder —
no new builder type and no new comparison/hash logic.

What changes are included in this PR?

• Accept Duration(_) in group_column_supported_type (all four TimeUnits are
  valid Arrow types, unlike the restricted Time32/Time64 set).
• Dispatch the four Duration*Type units in make_group_column.
• Extend the group_column_supported_type ↔ make_group_column consistency fuzz
  with all four Duration units.
• Add a (Duration, Int32) group-count benchmark to benches/multi_group_by.rs.

Are these changes tested?

Yes.

• New unit test test_group_values_column_duration: a Duration key stays on the
  GroupValuesColumn path, dedups equal durations (including nulls), and
  round-trips with the Duration output type preserved (not the bare i64).
• The consistency fuzz now asserts every Duration unit routes through the
  dispatcher.
• New single- and multi-column Duration GROUP BY coverage in aggregate.slt.

Are there any user-facing changes?

No API changes. GROUP BY queries with a Duration key now use the column-wise
fast path instead of the row-encoded fallback; results are unchanged.