CopyContext: Replace src_uri, dst_uri by src, dst

Allow to pass ready-made FileContext objects to CopyContext's destructor so it doesn't need to instantiate them itself.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/cmds/posix/tar/CmdExtract.py

@@ -21,7 +21,5 @@ class CmdExtract(Cmd): # export
         parser.add_argument('dst', help='Destination root URI')
 
     async def _run(self, args: Namespace) -> None:
-        async with self.ctx(
-                dst_uri = args.dst,
-            ) as ctx:
+        async with self.ctx(dst=args.dst) as ctx:
             await ctx.extract(ctx.dst.root)