Add support for x-maintenance-intent in dune-project #29485

Job	Run time
Build microbenchmarks	2m 29s
Coq 8.16.1	7m 10s
Create local opam switch (macos-latest, 5)	6m 14s
Create local opam switch (macos-latest, 4.14)	5m 34s
Documentation	59s
Create local opam switch (ubuntu-latest, 5)	4m 51s
Format	1m 9s
Create local opam switch (ubuntu-latest, 4.14)	5m 5s
Build monorepo benchmark docker image	3m 46s
Nix (macos-latest)	2m 19s
Build (macos-latest, 5.1.x)	13m 46s
Nix (ubuntu-latest)	58s
Wasm_of_ocaml	10m 37s
Build (ubuntu-latest, 5.1.x)	10m 28s
Build (ocaml-variants.5.3.0+trunk, ubuntu-latest, true)	1m 4s
Build (4.14.x, ubuntu-latest, true)	1m 38s
Build (4.14.x, macos-latest, true)	2m 37s
Build (5.1.x, macos-13, true)	5m 20s
Build (ocaml-base-compiler.4.14.2,system-msvc, windows-latest)	14m 47s
Build (ocaml-base-compiler.5.1.1,system-mingw, windows-latest)	8m 36s
Build (4.08.x, ubuntu-latest, true)	1m 31s
Build (4.04.x, ubuntu-latest, true, true)	4m 28s
Build (4.02.x, ubuntu-latest, true)	4m 8s
	1h 59m 34s

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