test(rest): pin the compiled list-view group-header and row-page queries through POST /data/:object/query (#15548)

The spec half of server-side list-view grouping (#14556) compiles a grouped
list view into an aggregate header query and a per-group row page, pinned only
against a reducer local to its own test file. This adds the platform half: the
COMPILED queries are posted through the existing door and answered by the real
chain (RestServer -> protocol.findData -> engine.aggregate -> sqlite SqlDriver),
on BOTH faces `ObjectQL.aggregate` forks between -- driver-sql's native GROUP BY
and `applyInMemoryAggregation` -- with the fork driven by shadowing
`driver.aggregate` over one driver instance and one seeded database, and
asserted by call counters rather than assumed.

Pins the card's fixture (186 rows, five units 86/61/31/7/1) in both row orders,
a two-level groupBy, the `depth: 1` outer level, the empty group keyed null
with its `$null` row page, one derived summary (count_filled of a nullable
field), the view filter reaching the header numbers, and 86 rows paging as
[50, 36] with 86 distinct ids.

No route, no wire shape and no behaviour changes: this is a pin.

Refs #15330


Claude-Session: https://claude.ai/code/session_01D47qPfEWVPmhguWgBZCi5N

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-litant