pg qrep: avro schema nullable by default

[serprex]

alternative to #3613

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
1304	2	1302	129

View the full list of 2 ❄️ flaky test(s)

github.com/PeerDB-io/peerdb/flow/e2e::TestGenericBQ

Flake rate in main: 30.56% (Passed 25 times, Failed 11 times)

Stack Traces | 0s run time

=== RUN   TestGenericBQ
=== PAUSE TestGenericBQ
=== CONT  TestGenericBQ
--- FAIL: TestGenericBQ (0.00s)
2025/10/17 21:02:51 INFO Received AWS credentials from peer for connector: ci x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}
2025/10/17 21:02:51 INFO Received AWS credentials from peer for connector: clickhouse x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN}

github.com/PeerDB-io/peerdb/flow/e2e::TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting

Flake rate in main: 30.56% (Passed 25 times, Failed 11 times)

Stack Traces | 33.6s run time

=== RUN   TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
=== PAUSE TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
=== CONT  TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
    generic_test.go:739: UNEXPECTED STATUS TIMEOUT STATUS_SNAPSHOT
    bigquery.go:86: begin tearing down postgres schema bq_1hmqnyfp_20251017210116
--- FAIL: TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting (33.57s)

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