Add CIP Kernel configuration support

Issue description

CIP support is driven by the configurations defined in the cip-kernel-config repository.

Currently KernelCI uses the in-tree defconfig, plus various config fragments when configuring the Linux kernel.

CIP would like to change this to use the configurations defined in cip-kernel-config.
Specifically we'd like to test with the "merged" configs that have been created; one for each architecture, e.g. 6.1.y-cip/arm64/cip_merged_defconfig

Useful links

• cip-kernel-config

Acceptance criteria

• Each cip_merged_defconfig in cip-kernel-config is converted into a .config fragment derived from the relevant in-tree defconfig
• KernelCI uses defconfig plus the correct kernel config fragment (version & arch) when building the CIP tree