import: opam: Move tests to tests/import/opam.scm.

* tests/opam.scm: Move to tests/import/opam.scm.
* Makefile.am: Refresh it.
* CODEOWNERS: Refresh it.
* etc/teams.scm: Refresh it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

Makefile.am

@@ -572,6 +572,7 @@ SCM_TESTS =					\
   tests/import/gem.scm				\
   tests/import/git.scm				\
   tests/import/hackage.scm			\
+  tests/import/opam.scm				\
   tests/import/pypi.scm				\
   tests/home-import.scm				\
   tests/home-services.scm			\
@@ -589,7 +590,6 @@ SCM_TESTS =					\
   tests/nar.scm				\
   tests/npm-binary.scm				\
   tests/networking.scm				\
-  tests/opam.scm				\
   tests/openpgp.scm				\
   tests/packages.scm				\
   tests/pack.scm				\