replaced `HashMap` / `HashSet` with `IndexMap` / `IndexSet` #611

Job	Run time
Run PostgreSQL tests (ubuntu-latest)	5m 21s
Install warg CLI	4m 57s
Run tests (ubuntu-latest)	4m 7s
Format source code	3s
Run tests (macos-latest)	5m 46s
Run tests (windows-latest)	6m 25s
	26m 39s

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