This change moves our e2e tests into a separate package to make room for proper unit and integration tests.
This is Phase 1 described in #371.
Changes:
Makefile has separate directives to run unit/integration tests and e2e tests,
CI runs unit/integration tests first and then e2e tests,
E2e tests are in reliability order, i.e. the least reliable tests are run in the end to be sure that nothing else is broken,
Some tests are fixed or quarantined.
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