`dune tools install` should take multiple package arguments

[shonfeder]

Desired Behavior

dune tools install a b c

should install the dev tools a, b, and c.

Example

E.g.,

dune tools install ocamllsp ocamlformat

Instead, this currently reports

dune: too many arguments, don't know what to do with 'ocamlformat'

[shonfeder]

Just looked at this with @Sudha247 who explained that the current Cmdliner term treats each installable as a subcommand for some reason, constructed here:

https://github.com/ocaml/dune/blob/84e0722baf93a763fb82fb3d234ead55e930ab6a/bin/tools/tools_common.ml#L114-L125

We think there should be no reason this can't be rewritten to instead take a list of arguments here:

https://github.com/ocaml/dune/blob/84e0722baf93a763fb82fb3d234ead55e930ab6a/bin/tools/group.ml#L23-L30

[Sudha247]

I have a patch for this here: https://github.com/Sudha247/dune/tree/dune-tools-multiple-arguments. It includes a cram test, which currently fails because it's unable to find the subsequent packages after the first package.

Install the dev tools
 |
 |$ dune tools install ocamllsp ocamlformat
 |  $ dune tools install ocamlformat ocamllsp
+|  Solution for _build/.dev-tools.locks/ocamlformat:
+|  - ocamlformat.0.0.1
+|  Solution for _build/.dev-tools.locks/ocaml-lsp-server:
+|  - ocaml.5.2.0
+|  - ocaml-lsp-server.0.0.1
+|  Error: Unknown package this "ocaml-lsp-server"
+|  I didn't find the package

We looked at it a bit with @Leonidas-from-XIV, and concluded that the solver is not able to find the second package from the DB here: https://github.com/ocaml/dune/blob/7c53739170c4131e3ca58ca522b02174db59d2da/src/dune_rules/pkg_rules.ml#L1460-L1462

However, I'm not sure whether this is the expected behaviour. I'll dig further into this, and if anyone has thoughts that would be useful.