Add an updated Kconfiglib

Add some changes to allow this library to work with Zephyr:

- Ability to have Kconfig files in multiple projects directories
- Ability to ignore variable expansion failures, since there are so many
   Kconfig variables in Zephyr

These changes have been sent upstream here:

   ulfalizer/Kconfiglib#112

and to Zephyr here:

zephyrproject-rtos/zephyr#42233

so this also includes the one Zephyr-local commit:

   66d1b3ce106 kconfig: kconfiglib.py: Backup files only

All three commits are based on Kconfiglib 14.1.0

BUG=b:181323955
BRANCH=none
TEST=python3 util/test_kconfig_check.py

Signed-off-by: Simon Glass <[email protected]>
Change-Id: Iac24a90fe3707cacab40d45210addc663bb17f60
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3390708
Reviewed-by: Jack Rosenthal <[email protected]>