[new release] vchan (3 packages) (6.0.2)

[hannesm]

Xen Vchan implementation

• Project page: https://github.com/mirage/ocaml-vchan
• Documentation: https://mirage.github.io/ocaml-vchan

CHANGES:

• adapt to mirage-flow 4 changes (add shutdown, alias to close) (Mirage flow 4, no ppx_cstruct, no sexplib, updates mirage/ocaml-vchan#143 @hannesm)
• remove ppx_cstruct and sexplib and ppx_sexp_conv dependencies (Mirage flow 4, no ppx_cstruct, no sexplib, updates mirage/ocaml-vchan#143 @hannesm)
• update to cmdliner 1.1.0 changes (Mirage flow 4, no ppx_cstruct, no sexplib, updates mirage/ocaml-vchan#143 @hannesm)
• use oUnit2 (use ounit2 mirage/ocaml-vchan#141 @Alessandro-Barbieri)

[hannesm]

revdep fix (conduit-mirage): #25771