[cli/enh] on 'shell' or migration command, use ipython if available

[web/test] drop dependency on third party cubes Drop dependency on cubicweb-file, cubicweb-blog and cubicweb-tag for cubicweb/web/test Copy required parts of cubes (schema, entities, views and hooks) into cubicweb/web/test/data/cubicweb-<cube> that make tests pass.

[test] drop dependency on third party cubes Drop dependency on cubicweb-file, cubicweb-localperms, cubicweb-tag and cubicweb-comment for cubicweb.test and cubicweb.sobjects.test Move cubicweb/test/data/libpython/cubicweb_* to cubicweb/test/data, so it's included in PYTHONPATH. Add missing parts of schema, entities, views, hooks that make tests pass.

[test] drop CubicWebConfigurationWithLegacyCubesTC This is used to test legacy cube import which is planned for removal in cubicweb 3.27, so drop the code.

[test] drop unittest_cubes.py This is used to test legacy cube import which is planned for removal in cubicweb 3.27, so drop the code.

[server/test] do not depend on third party cubes Drop requirement of basket, card, comment, file, localperms and tag cubes for cubicweb.server tests. Copy needed part of schema, entities, views, hooks into the cubicweb/server/test/data directory (which is included in PYTHONPATH for CubicWebTC tests). For migration tests which use different "datapath", use symlinks to have dependent cubes importables.

[server/test] drop unused variable initialization in OperationsTC.setUp() Variable "self.hm" is unused