[seekdb][memory] Add main memory module statistics view

[hnwyllmm]

Task Description

Existing __all_virtual_memory_info / V$OB_MEMORY rely on obmalloc label statistics, making it impossible to intuitively display the memory usage and limits of main modules after obmalloc is removed.

MySQL [oceanbase]> select * from v$ob_memory order by hold desc;
+--------------+-----------+----------+-------------+
| MOD_NAME | HOLD | USED | MEM_LIMIT |
+--------------+-----------+----------+-------------+
| KV_CACHE | 216156320 | 5673024 | 37006867660 |
| PLAN_CACHE | 24867761 | 24867761 | 42949672 |
| MEMSTORE | 20798160 | 20798160 | 1717986918 |
| STORAGE_META | 3416704 | 3147984 | NULL |
| TX_DATA | 2284736 | 2284736 | 858993459 |
| SCHEMA | 2079744 | 1257680 | NULL |
| PS_CACHE | 589872 | 589872 | 21474836 |
| MDS | 476160 | 476160 | 429496729 |
| VECTOR | 2624 | 2624 | 1717986918 |
| SQL_WORKAREA | 0 | 0 | 107374180 |
| DTL | 0 | 0 | NULL |
| TMP_FILE | 0 | 0 | 43524096 |
+--------------+-----------+----------+-------------+
12 rows in set (0.005 sec)

Solution Description

Adjusted __all_virtual_memory_info and V$OB_MEMORY to have four columns: MOD_NAME, HOLD, USED, MEM_LIMIT, fixed to aggregate 12 modules: KV Cache, Plan/PS Cache, MemStore, TX_DATA, MDS, Storage Meta, Schema, Vector, SQL Workarea, DTL, and Tmp File. Added a narrow-scope module getter, preserving the native statistical scope of each module. Modules without a valid limit return NULL, and no default ordering is provided. Migrated existing tests/golden files and cleaned up isolated results and assertions that depended on the old label statistics.

Passed Regressions

• ob-make ob_server
• CARGO_NET_OFFLINE=true ob-make seekdb
• New binary isolated instance verification: 12 rows with unique module names, HOLD >= USED >= 0, MEM_LIMIT NULL rules correct
• Passed 30 consecutive aggregation self-checks
• PS_CACHE cross-checked with __all_virtual_ps_stat is consistent
• No new dedicated mysqltest added; mysqltest was not run locally

Upgrade Compatibility

Directly replaces the old obmalloc virtual table contract, deleting old fields like ctx/label/count. Queries dependent on the old fields need to migrate to the new four-column module aggregation interface.

Other Information

This MR only contains commit 03a64f8fa00; 2 untracked files are not within the review scope. V$OB_MEMORY does not guarantee a default row order.

Release Note

[hnwyllmm]

The mapping Dima issue is to add memory statistics views for each major memory module.