Add startup postgresConfig and WAL-compatible pgoutput support

[sorenbs]

Summary

This PR enables reliable logical WAL support for @electric-sql/pglite consumers (specifically ppg-dev) by adding startup-time Postgres config support and wiring pgoutput-compatible symbol exports.

ppg-dev depends on setting postmaster-level GUCs at startup (wal_level=logical, replication slot/sender limits), and on loading pgoutput for logical decoding. This PR makes that work end-to-end.

Changes

1. Add startup Postgres config API in pglite:

• PGliteOptions.postgresConfig?: Record<string, string | number | boolean>
• Config is serialized and passed to backend startup as PGLITE_POSTGRES_CONFIG.

2. Apply startup config inside wasm backend (postgres-pglite submodule):

• Parse PGLITE_POSTGRES_CONFIG.
• Call SetConfigOption(..., PGC_POSTMASTER, PGC_S_ARGV) before normal startup proceeds in both startup paths.

3. Export pgoutput-required core symbols/globals:

• Add pgoutput-required imports to included.pglite.imports so the main wasm exports what pgoutput.so needs at load time.

4. Add shutdown guard:

• Handle numeric Infinity sentinel on close (emscripten shutdown anomaly path) so close remains successful.

5. Add test coverage:

• New packages/pglite/tests/postgres-config.test.ts verifies startup application of:
  • wal_level=logical
  • max_replication_slots
  • max_wal_senders

Validation

• pglite tests:
  • vitest tests/postgres-config.test.ts tests/basic.test.ts --run pass.
• WAL smoke:
  • pg_create_logical_replication_slot(..., 'pgoutput') succeeds.
  • pg_logical_slot_get_binary_changes(...) returns changes.
• ppg-dev:
  • WAL integration tests pass in dev/server/src/db.wal.test.ts.

Dependency

This PR depends on the corresponding prisma/postgres-pglite branch/PR that contains the wasm/backend symbol-export and startup-config plumbing. electric-sql/postgres-pglite#64