do not build query filter with or: [] when all records are successfully upserted, for return_skipped_upsert?: true

[DohanKim]

Problem

When using Ash.bulk_create/4 with the AshPostgres data layer, upsert?: true, and return_skipped_upsert?: true, if all records are successfully inserted (none skipped due to upsert conditions), the code builds a filter with or: [] to fetch skipped records, which triggers a crash:

  ** (FunctionClauseError) no function clause matching in Ash.Filter.parse_and_join/3
      (ash 3.9.0) lib/ash/filter/filter.ex:4711: Ash.Filter.parse_and_join([], :or, %{...})

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[zachdaniel]

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