* Enable "vela show" to support namespaced capability
Provide option `-namespace`, if not set, the default namespace
is default. If not found, as by default, capabilities are located in
vela-system, it will continue to retrieve the capability in
vela-system directory.
Fix#1520
* add e2e tests
* Address comments: Revert env context back
Get namespace from env, instead of adding option "-namespace"
* fix unittest issue
* Address comments
Co-authored-by: Jianbo Sun <wonderflow.sun@gmail.com>
* fix e2e
Co-authored-by: Jianbo Sun <wonderflow.sun@gmail.com>