The aggregation multiversion fuzzer generated a `$accumulator` whose JavaScript state called comparatorless `Array.sort()` on heterogeneous values containing BSON `Date` objects.

JavaScript's default array sort implicitly stringifies values. `Date.toString()` uses the host's local timezone, causing different result ordering between legacy MozJS and the MongoDB 9.0 WASM-based JavaScript engine. This caused the failure reported in BF-45664(https://jira.mongodb.org/browse/BF-45664).

Update the aggregation fuzzer so generated queries do not depend on implicit local-time `Date` stringification. In particular, avoid generating comparatorless sorts over values that may contain Dates, or generate an explicit timezone-independent comparison instead.

The change should be limited to fuzzer generation. Do not change server-side JavaScript compatibility behavior as part of this ticket.

Acceptance Criteria

• The aggregation fuzzer no longer generates comparatorless JavaScript `Array.sort()` calls over heterogeneous values that may contain `Date` objects.
• Any generated Date comparisons or serializations use timezone-independent behavior, such as `getTime()` or `toISOString()`, with an explicit comparator where needed.
• Add a regression test covering the previously failing generated pattern.
• Verify the regression test produces identical results under UTC and a non-UTC timezone.
• Confirm the existing aggregation fuzzer coverage remains enabled for timezone-aware MQL date operators.
• Link BF-45664(https://jira.mongodb.org/browse/BF-45664).