ci(e2e): delete the host Podman lane after #5297 PR6 #5423

User Story

I maintain OpenShell's CI and am retiring the old e2e/rust system (#5281). Once the migration has moved its last tests, I need the host Podman lane gone, so Branch E2E stops running duplicate tests on a bare runner.

Description

The Branch E2E job podman-e2e / E2E (rust-podman-ci, ubuntu-26.04) runs mise run e2e:podman:ci, which takes about 13 minutes. It runs openshell-conformance and 23 e2e/rust binaries. tmachine already runs the conformance tests and 17 of those binaries. Six binaries run only here:

• provider_token_exchange
• podman_corporate_proxy
• podman_gateway_start
• local_driver_token_restart
• driver_config_volume
• otlp_relay: its collector cases need the OTLP endpoint the wrapper sets.

The #5297 plan ports all six: driver_config_volume and local_driver_token_restart in PR5, the rest in PR6. After PR6, the lane covers nothing unique, so delete it in one step then. Trimming it earlier was tried in #5424 and closed: it added a second list to keep in sync while the migration moves these tests. That PR's description has the full comparison.

Context

• Parent: test: retire the old e2e test system onto testkit #5281. Migration plan: test(e2e): decide which e2e/rust tests to port and in what order #5297.
• Verification (run 42694439028): ci(e2e): trim the host Podman lane to tests tmachine can't run yet #5424 description.

Definition of Done

• test(e2e): decide which e2e/rust tests to port and in what order #5297 PR5 and PR6 have landed.
• The podman-e2e job and its entry in Core E2E result are deleted from .github/workflows/branch-e2e.yml.
• The e2e:podman:ci task, PODMAN_CI_TESTS and the test-set handling in e2e/rust/e2e-podman.sh are deleted, unless the last migration PR has already deleted them.
• The "wrapper lane" comments in tests/tmachine/artifacts.nix are gone or updated.