scripts/wic: fix calling wic ls|cp|rm|write hung in bitbake task

scripts/wic: fix calling wic ls|cp|rm|write hung in bitbake task

While calling wic ls/cp/rm/write in bitbake task along with do_image_wic,
it hung without return.

Due to commit [2255f28b57 wic: add WIC_SECTOR_SIZE variable][1] applied,
It calls get_bitbake_var in `wic ls|cp|rm|write' to define sector size.
By default, get_bitbake_var starts a `bitbake -e' to get variables which
triggers nested bitbake in this situation

Refer `wic create', adds option --vars and --image-name to support to
read bitbake variables from <image>.env files

NOTE: This commit does not add -e for `wic write' to avoid confliction
with existed option -e/--expand

[1] https://github.com/openembedded/openembedded-core/commit/2255f28b579bc5db4138bcacbb829661ae0ee721

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>