BUG - building with a board revision does not correctly add board overlays

[TjazVracko]

Describe the bug

If I have a board that requires qualifiers in the build command, specifying the board revision stops adding a board specific overlay to the build.

Firmware/Software Version

0.25.2

To Reproduce

Example:

1. Have a board named plank that uses /mcu/ns and /mcu qualifiers.
2. I have board revisions 1.0.0 (default) and 1.1.0.
3. I then also have a conf folder with common.conf and plank_mcu_ns.conf.

If I build without specifying the revision: ˙east --echo build -b plank/mcu/ns`. The echoed build command is:

/home/.../nrfutil toolchain-manager launch --ncs-version v2.8.0 -- west build -b plank/mcu/ns -- -DCONF_FILE=conf/common.conf -DOVERLAY_CONFIG="conf/plank_mcu_ns.conf  -DEAST_BUILD_TYPE="release""

If I build with specifying the revision: ˙east --echo build -b plank@1.0.0/mcu/ns`. The echoed build command is:

/home/.../nrfutil toolchain-manager launch --ncs-version v2.8.0 -- west build -b plank/mcu/ns -- -DCONF_FILE=conf/common.conf  -DEAST_BUILD_TYPE="release""

Additional context

I think the error is here.

When we had the old hardware model, you would specify the revision at the end:
``east build -b plank_mcu_ns@1.0.0`

But now, it happens "in the middle":
``east build -b plank@1.0.0/mcu/ns`

The code linked above assumes that the revision is at the end.

Workaround

If I rename plank_mcu_ns.conf to plank.conf, it gets included in the build.
This is fine for my specific project, but is not a general solution.

Notes/Comments

We are drifting further and further apart from how zephyr collects dts and conf files and how east does it.
I feel like it is time to move to using snippets and stuff from Zephyr :(