imagebuilder: implement STRIP_ABI option for manifest target

imagebuilder: implement STRIP_ABI option for manifest target

When using apk as the package manager, imagebuilder make command

    make manifest STRIP_ABI=1

does not strip package names of their ABI-version suffix.  The ASU
server relies on this to validate builds, so many snapshot build
requests are failing.

Fix this by using the already existing package data parser in
make-index-json.py and augment it to write the result in manifest
format.

Fixes: https://github.com/openwrt/openwrt/issues/19274
Signed-off-by: Eric Fahlgren <ericfahlgren@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/19278
Signed-off-by: Robert Marko <robimarko@gmail.com>