The flaky integration test job collects changed test modules from the PR
diff and asks `get_parallel_sequential_tests_to_run` to match each one
against the parallel/sequential module lists. Without `no_strict`, a
changed test that has been filtered out (e.g. by the private fork's
`SKIP_LIST` in `ci/jobs/scripts/integration_tests_configs.py`) trips
`assert matched, f"Test [{test_arg}] not found"`, killing the whole job.

This is the same concern that already justifies `no_strict=True` for
targeted checks (a CIDB-recorded test may be deleted or renamed before
the job runs). Extend the relaxation to flaky checks so a SKIP_LIST'd
test is silently dropped — the private fork has an explicit empty-result
handler that turns the resulting empty test list into a `SKIPPED` job.

This unblocks `CH Inc sync` on PRs that modify any test in `SKIP_LIST`
(e.g. `test_kafka_bad_messages`), such as
#100276 — its sync PR
ClickHouse/clickhouse-private#53191 failed in
`Integration tests (amd_asan_ubsan, flaky)` with
`AssertionError: Test [test_kafka_bad_messages/test.py] not found`.

The prior commit relaxed `get_parallel_sequential_tests_to_run` with
`no_strict=True` for flaky checks so a `SKIP_LIST`-filtered test would no
longer trip the `Test [...] not found` assertion. But the empty-selection
path was only handled for targeted checks: if both module lists came out
empty for a flaky check, no `pytest` run happened and
`Result.create_from(results=[], ...)` ended the job with `ERROR` rather
than `SKIPPED`.

Extend the empty-selection short-circuit to flaky checks so the job is
reported as `SKIPPED` with an explanatory `info` message.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>