test(pkg): show dune exec run binaries from project dependencies

[Sudha247]

Description

I discovered this feature while working on #12914, and found that we currently don't have a test for it. This test essentially shows that it is currently possible to run a binary that is shipped with a dependency. I have examined more behaviors of this, which I'll try to add in follow-up PRs.

This is possible owing to:

dune/src/dune_rules/pkg_rules.ml

Lines 2571 to 2588 in 59105f8

	let which context =
	let artifacts_and_deps =
	Memo.lazy_
	~name:"lock-directory-binaries"
	~human_readable_description:(fun () ->
	Pp.textf
	"Loading all binaries in the lock directory for %S"
	(Context_name.to_string context))
	(fun () ->
	let+ { binaries; dep_info = _ } =
	all_project_deps context >>= Action_expander.Artifacts_and_deps.of_closure
	in
	binaries)
	in
	Staged.stage (fun program ->
	let+ artifacts = Memo.Lazy.force artifacts_and_deps in
	Filename.Map.find artifacts program)
	;;

Related Issue and Motivation

Relates to work to be done in #16185

Checklist

• Tests added, if applicable.
• Change log entry added for any user-facing changes. (NA)
• Documentation added for any user-facing changes. (NA)

[punchagan]

Seems reasonable. I've written a similar test as a part of my work for bin-narrowing in #15381. I wonder if it's better to eventually have my tests in the pkg/ directory instead of pkg/bin-narrowing. (I can fold my exec test into this one)