Add static analysis for defconfigs

It would be desirable for kernelci to do static analysis on the defconfigs, for example if a config option is removed:

https://github.com/torvalds/linux/commit/802b83205519e4253b873bef5c095b147cd69dad

but users of it remain:

https://github.com/torvalds/linux/blob/231825b2e1ff6ba799c5eaf396d3ab2354e37c6b/arch/arm64/configs/defconfig#L1355

then that should be raised in CI.

In the Yocto Project we have a tool which does this: https://git.yoctoproject.org/yocto-kernel-tools/tree/tools/symbol_why.py and we'd be happy to help because our kernel builds fail due to issues like this.

Start by reviewing the Yocto Project tool tools/symbol_why.py and the linked Linux commit and defconfig entry to understand the stale-config case. Then determine how kernelci-pipeline CI should run this analysis; done means references to removed config options in defconfigs are reported in CI.

Written by the indexing model from the issue text.