ec-test-cli: Remove `critical-section` dep when able

https://github.com/OpenDevicePartnership/odp-platform-common/pull/27 introduced the ec-test-cli and it also discovered a bug where debug builds won't build without a criticial-section implementation (it seemed to work in release build since the compiler could recognize critical-section related stuff as dead code).

This happens because the ec apps here depend on some of the service message dependencies, which transitively depend on embedded-services. embedded-services unconditionally pulls in the critical-section dep but requires the user to provide the critical section implementation.

Hence, in the above PR, I just used the std implementation. Should investigate if we can remove the embedded-services dep from all the deps we use here which will allow us to remove the ugly crtiical-section dep here.