refactor(pkg): use opam lib for stringifying relop #29478

Job	Run time
Documentation	1m 2s
Nix (macos-latest)	1m 57s
Coq 8.16.1	7m 32s
Nix (ubuntu-latest)	53s
Build (macos-latest, 5.1.x)	13m 47s
Format	1m 4s
Build (ubuntu-latest, 5.1.x)	8m 32s
Build (ocaml-variants.5.3.0+trunk, ubuntu-latest, true)	1m 18s
Wasm_of_ocaml	11m 1s
Build microbenchmarks	2m 34s
Build (4.14.x, ubuntu-latest, true)	1m 45s
Create local opam switch (macos-latest, 5)	5m 15s
Build (4.14.x, macos-latest, true)	2m 43s
Create local opam switch (macos-latest, 4.14)	5m 47s
Build (5.1.x, macos-13, true)	4m 22s
Build monorepo benchmark docker image	3m 41s
Create local opam switch (ubuntu-latest, 5)	10m 53s
Build (ocaml-base-compiler.4.14.2,system-msvc, windows-latest)	15m 17s
Build (ocaml-base-compiler.5.1.1,system-mingw, windows-latest)	9m 13s
Create local opam switch (ubuntu-latest, 4.14)	5m 2s
Build (4.08.x, ubuntu-latest, true)	1m 34s
Build (4.04.x, ubuntu-latest, true, true)	4m 33s
Build (4.02.x, ubuntu-latest, true)	4m 8s
	2h 3m 53s

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