Test PR 6521

graph: Re-enable postponed index creation in debug builds

The v0.44.0 disable patch hardcoded `postpone_attribute_index_creation`
to `false`, which broke three `relational::ddl_tests` (`generate_ddl`,
`generate_postponed_indexes`, `postponed_indexes_with_block_column`)
that exercise the postponed-index DDL path and relied on the prior
`cfg!(debug_assertions)` auto-on for that coverage.

Switch the field to `cfg!(debug_assertions)` so:

- Release builds (production): postponement stays off regardless of
  env var, matching the intent of the original disable.
- Debug builds (CI + dev): postponement is on, so the existing tests
  exercise the code path and pass.

The `GRAPH_POSTPONE_ATTRIBUTE_INDEX_CREATION` env var stays inert
(parsed but unused, hence the existing `#[allow(unused)]`).

Log block details on "Found no transaction for event" error

Log tx count at RPC fetch point in load_blocks_rpc

bigdecimal test

news: v0.43.0 release notes

Test only - do not use

Test only - do not use

news: v0.42.1 release notes

fix: extract file path from IPC URL in Transport::new_ipc (#6443)