Tests: MCUboot testing: Extend to more targets

[erwango]

Is your enhancement proposal related to a problem? Please describe.
(expanded by @PerMac) Tests for mcuboot have very restrictive means of filtering platform scope: platform_allow with only few boards https://github.com/zephyrproject-rtos/zephyr/blob/main/tests/boot/test_mcuboot/testcase.yaml
It prevents the testing on other boards which do support mcuboot. E.g. we have to use --force-platform in our internal CI to run tests on most of our (nrf) boards. This is inconvenient, since this flag messes with scope selection rules and causes issues in other places.

The task is to find such combination of required filters, based on dts and kconfigs, to allow for the most generic scope without the need of platform_allow. #53499 allowed for independent usage of kconfig and/or dts based filters. Maybe it can help with finding the proper combinations of filters?

Original request:
Is your enhancement proposal related to a problem? Please describe.
In #58109 a MCUBoot test variant was added to test platform with asserts.
This should be extended at least to STM32 targets compatible with mcuboot

[PerMac]

@erwango I want to open a similar request, but a more generic one. I.e. to modify all mcuboot tests and remove platform_allow since it is very restrictive, even though we are able to successfully run those tests on other platforms as well. Will you be fine if I edit this issue to a more generic one instead of opening a new one?

[erwango]

but a more generic one. I.e. to modify all mcuboot tests and remove platform_allow since it is very restrictive,

Great, I though about it, but didn't want to impact too much platform. Totally approving.

Will you be fine if I edit this issue to a more generic one instead of opening a new one?

Sure, go ahead

[PerMac]

#51448 was an attempt to resolve the issue. Some information can be found in comments there.
cc @danieldegrasse @nordicjm @de-nordic @d3zd3z @rerickson1 @str4t0m @gchwier @carlescufi

[erwango]

@PerMac I'm resetting the assignee as @Desvauxm-st is not the right person for such a wide change.