heptapod-ci: add a job to test the rust version of Mercurial

The rust version of Mercurial is not currently tested by anything else. So it
get quite important that developer runs it.

Differential Revision: https://phab.mercurial-scm.org/D8017
10 jobs for topic/stable/heptapod-ci in 34 minutes and 40 seconds (queued for 2 minutes and 52 seconds)
Name Stage Failure
failed
test-py2-pure Test
Skipped test-sparse-fsmonitor.t: skipped
Skipped test-sparse-revlog.t: missing artifact, run "/tmp/mercurial-ci/tests/artifacts/scripts/generate-churning-bundle.py"
Skipped test-sqlitestore.t: missing feature: sqlite3 module is available
Skipped test-verify-repo-operations.py: missing feature: allow slow tests (use --allow-slow-tests)
Skipped test-wireproto-exchangev2-shallow.t: missing feature: sqlite3 module is available
Failed test-subrepo-git.t: timed out
# Ran 832 tests, 71 skipped, 1 failed.
python hash seed: 1780978855
ERROR: Job failed: exit code 1
failed
test-py3-pure Test
Skipped test-sparse-fsmonitor.t: skipped
Skipped test-sparse-revlog.t: missing artifact, run "/tmp/mercurial-ci/tests/artifacts/scripts/generate-churning-bundle.py"
Skipped test-sqlitestore.t: missing feature: sqlite3 module is available
Skipped test-verify-repo-operations.py: missing feature: allow slow tests (use --allow-slow-tests)
Skipped test-wireproto-exchangev2-shallow.t: missing feature: sqlite3 module is available
Failed test-remotefilelog-bgprefetch.t: output changed
# Ran 826 tests, 77 skipped, 1 failed.
python hash seed: 669608707
ERROR: Job failed: exit code 1
failed
test-py2-rust Test
Skipped test-sparse-fsmonitor.t: skipped
Skipped test-sparse-revlog.t: missing artifact, run "/tmp/mercurial-ci/tests/artifacts/scripts/generate-churning-bundle.py"
Skipped test-sqlitestore.t: missing feature: sqlite3 module is available
Skipped test-verify-repo-operations.py: missing feature: allow slow tests (use --allow-slow-tests)
Skipped test-wireproto-exchangev2-shallow.t: missing feature: sqlite3 module is available
Failed test-amend.t#obsstore-off: output changed
# Ran 836 tests, 67 skipped, 1 failed.
python hash seed: 112390689
ERROR: Job failed: exit code 1