[meta] Improve system tests robustness

[marc-gr]

Several integrations that rely on external APIs use stream as their test services to build mocks and run system tests.

There are some blind spots when it comes to detecting config errors that could lead to wrong pagination, infinite pagination loops, etc. mainly caused by the inability of elastic-package to detect anything else than is there any data? in the data stream or is there the expected number of events? if assert.hit_count is set, which makes things better but is not enough.

As part of an effort to improve system tests robustness some things could be improved:

• Add an option to data_stream/_dev/test/system/config.yml to fail the tests if the test services exit unsuccessfully. Add ignore_service_error flag to selectively ignore test service errored containers #1540
• Add option to http mock to fail if it gets a request that does not match stream#61
• Add the concept of sequences in http mock stream#62

Once this is done we can leverage these new behavior for system tests that require it.