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](https://gitlab.com/cip-project/cip-kernel/cip-kernel-config/-/blob/master/6.1.y-cip/arm64/cip_merged_defconfig)
## Useful links
* [cip-kernel-config](https://gitlab.com/cip-project/cip-kernel/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
issue