Add automated test for checking OpenWrt ImageBuilder

[nikhil-zinjurde-imgtec]

Acceptance Criteria:

• Can generate identical platform image for specified profile
• Can generate image with extra packages included (to be defined and reviewed in design stage)
• Can generate image with overridden files
• Images generated using ImageBuilder run on Ci40 and pass boardfarm tests
• Test is run only when BUILD_TOOLS and ALL_PACKAGES build parameters are checked