[CI] Register PIC unit tests in CPU CI

[morluto]

Problem

PIC has unit tests for cache operations, eviction, scheduling, request fields, and related helpers, but the suite lives under python/sglang/test/srt/pic. That path is outside the registered CPU unit-test tree, so the normal CI selection does not exercise PIC.

python/sglang/test/srt/pic
             |
             v
      outside registry
             |
             v
      not selected by CI

This leaves PIC changes without a regression gate even though test cases already exist.

Evidence

Registering the existing tests under test/registered/unit/pic exposed stale fixtures and assertions:

22 failed, 41 passed, 1 skipped

After updating those tests to the current interfaces, the registered suite contains 24 files and reports:

63 passed

Desired outcome

PIC unit tests should be part of the registered CPU test suite, use the current PIC interfaces, and run through the repository's normal CI selection.