CI Testing Improvements and Implementation of Storage Tests

This MR contains:

1. Preparations and minor improvements of the testing setup along the lines of meta-ked-bsp!70 (merged)
2. Extension for pytest to parse a YAML configuration file with target-specific test selection and parameters including simple unit tests for the parser code
   Extension was moved to its own repo to be reused by different projects: https://git.kontron-electronics.de/sw/ked/pytest-yaml-params.
3. Implementation of MMC and SPI NOR tests as part of https://git.kontron-electronics.de/sw/ked/plan/plan-ked-bootloader/-/issues/2

As this is quite a lot of changes, we can also easily split this up into multiple MRs if required.

For reference here is a resulting test report in GitLab with the MMC tests run on the BL i.MX8MM in the rack: https://git.kontron-electronics.de/sw/ked/meta-ked-bootloader/-/pipelines/21040/test_report?job_name=bootloader%3Atest%3Abl-mx8mm.

CC: @estoll @jgkling @jbauknecht