branch-4.0: [fix](test) deflake test_curd_wlg and adapt test_single_replica_compaction_with_format_v2 to V3 default

[morningman]

Proposed changes

Fix two pre-existing branch-4.0 P0 regression-test failures (surfaced by an internal P0 build). Both are test-side issues, unrelated to product code.

1. test_single_replica_compaction_with_format_v2 — failed 100% on master/4.1/4.0, passes on 3.0

#57252 changed the FE default inverted_index_storage_format from V2 to V3, but this test still created its table without pinning the property and asserted check_nested_index_file(..., 2, 3, "V2") with a hardcoded rowset count. Its sibling *_format_v2 tests (test_cumulative_compaction_with_format_v2, test_mow_table_with_format_v2) were already migrated to a dynamic rowset count + "V3"; this one was missed.

Fix: derive the post-compaction rowset count per tablet via be_show_tablet_status and assert "V3", mirroring the sibling tests.

2. test_curd_wlg — flaky

The bypass_group (max_concurrency=0) check expects select count(1) from wlg_test_table to be rejected with query waiting queue is full. That identical query is run repeatedly earlier in the suite, so it can be served from the FE SQL result cache, which returns before a Coordinator is built and never enters the query queue — so the rejection never fires and the assertion sees no exception (but meet 'null').

Fix: disable the SQL cache (set enable_sql_cache=false) around this assertion so the query actually executes and hits the queue, then restore it.

Further comments

Test-only changes. Cannot be verified locally (needs a deployed cluster with >= 2 BEs); please verify via CI.

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[morningman]

run buildall