ci: Use zephyrproject-rtos/action-s3-cache@v1.2.0

This commit updates the CI workflows to use the S3 cache action v1.2.0,
which is based on node.js 16 and @actions/core 1.10.0, in preparation
for the upcoming removal of the deprecated GitHub features.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>