core-image, populate_sdk_base: Add zsh-completion-pkgs image feature

core-image, populate_sdk_base: Add zsh-completion-pkgs image feature

Add a zsh-completion-pkgs image feature to install *-zsh-completion
packages into an image. This is similar to the existing
bash-completion-pkgs feature.

Suggested-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Adam Nilsson <Adam.X.Nilsson@axis.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>