[improve] Improve LogRealTimeAlertE2eTest group alert flakiness

[Duansg]

What's changed?

CI failure on LogRealTimeAlertE2eTest.testRealTimeLogAlertWithGroupAlert: ConditionTimeout after 60s, group alert never captured.

The alert pipeline has a hard-coded 30s watermark delay in TimeService, so a 10s window can't close until maxEventTs ≥ windowEnd + 30s. Combined with Vector's 5s batch interval and the 5s watermark broadcast cycle, the first group alert can't fire before ~46s after Vector starts — leaving only ~14s of headroom in a 60s budget, which CI scheduling jitter consumes.

Changes

• LogRealTimeAlertE2eTest.java: group test budget 60s → TEST_WAIT_TIMEOUT (120s), matching the individual test.
• vector.yml: batch.timeout_secs: 5 → 1, so maxEventTs advances each second and windows close sooner.
• Local: 2 tests pass in 82s.

Checklist

• I have read the Contributing Guide
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

Add or update API

• I have added the necessary e2e tests and all cases have passed.