Replace "test strategies" with direct message testing

[sosnovsky]

          As this PR enhances the mock google storage in a way that sent messages become visible to the extension, these tests start to interfere with each other if run under the same account -- the backup message is visible to other tests. We should isolate the sent messages between the tests (and, if I understand @tomholub idea correctly), we should generally hide messages not related to the test.

So is this part of #5142 or a separate task?
We should also configure "test strategy" behavior explicitly via the configuration in the beginning of each test (currently done in TestBySubjectStrategyContext)
Let's do that after the merging of this PR?

Originally posted by @rrrooommmaaa in #5069 (comment)

[sosnovsky]

pre-last part of #4494

[rrrooommmaaa]

Not last.
There is also test.after.always('evaluate Catch.reportErr errors' with custom errors that are expected for specific tests

[sosnovsky]

Not last.
There is also test.after.always('evaluate Catch.reportErr errors' with custom errors that are expected for specific tests

Thanks, I missed it