rename all remaining packages to internal/ (#12418)

This is to ensure that there are no projects
that try to import `minio/minio/pkg` into
their own repo. Any such common packages should
go to `https://github.com/minio/pkg`

internal/dsync/.gitignore

@@ -0,0 +1,3 @@
+dsync.test
+coverage.txt
+*.out