Semantics of messages in 'expect'

[elBoberido]

In my last PR is described the actual expected result in the expect call of the expected and optional, e.g. This is okay since Foo is guaranteed but I was made aware that in iceoryx it was mainly used to describe the unexpected outcome, e.g. Failed because Foo invariant is broken. From my experience with Rust I'm more used to the former semantics, i.e. describe what is expected to happen. This can also be used instead of comments and as justification why expect is called instead of doing some error handling.

What do you think about changing the semantics of the expect message to describe why it is safe to call expect and also adjust the log output to something like

[FATAL] Expected 'This is okay since Foo is guaranteed' but failed

I would volunteer to change the current strings in iceoryx.

Originally posted by @elBoberido in #2029