[Bug]: Ubuntu UT outer timeout with Test_StorageUsageCache active

## CI failure

Matrixone CI / UT Test on Ubuntu/x86 failed in [run 33368047125, job 99412781316](https://github.com/matrixorigin/matrixone/actions/runs/33368047125/job/99412781316) for PR #27715 at head `7a24d186c7fbf2afd17df0616efc6740ee0b77c3`.

The exact CI command was:

```text
time make ut UT_CONFIGURED=1 UT_PARALLEL=8 UT_TIMEOUT=40 UT_SHARD=all
```

The terminal signature was the outer `timeout 90m` ending with `make: *** [Makefile:497: ut] Error 124`. The active-case diagnostic immediately before termination was:

```text
[active_ut_cases] active UT case: package=github.com/matrixorigin/matrixone/pkg/vm/engine/tae/db/test test=Test_StorageUsageCache state=run started=2026-08-31T08:57:13.400995134Z
make: *** [Makefile:497: ut] Error 124
```

There was no compile, type, static-check, assertion, panic, or race report in the failed job log.

## Attribution evidence

The PR changes Iceberg lifecycle, SQL/frontend, upgrade, runner, RFC, and Iceberg E2E files; it does not modify `pkg/vm/engine/tae/db/test` or `Test_StorageUsageCache`. The exact test body exercises `logtail.StorageUsageCache`; no changed Iceberg lifecycle function is called by that test.

Using the repository CGo wrapper and the same short/race mode as this UT group, all six isolated runs passed:

```text
.agents/skills/mo-dev/scripts/mo-cgo-test -short -race -v -count=1 -timeout=40m -run ^Test_StorageUsageCache$ ./pkg/vm/engine/tae/db/test
```

- PR head `7a24d186c7fbf2afd17df0616efc6740ee0b77c3`: 3/3 passed (about 3.5–3.6 s each).
- Clean current official `up/main` `aa7b969f55e655f3f201fd3337589d070f994494`: 3/3 passed (about 3.6–3.7 s each).

The clean-main control used a detached worktree and matching verified local CGo inputs; no source modifications were made. This is a flaky-candidate report for the outer suite timeout/runner scheduling or suite-duration condition, not evidence that this small test deterministically hangs.

## Reproduction

Run the command above in the Ubuntu UT race configuration, or run the full CI command shown above and retain the active-case diagnostics when its 90-minute outer budget expires.