Physically dropping table is slow sometime

[JaySon-Huang]

Bug Report

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In #8721, we introduce a rule that: "if the regions of a given table is not totally removed from TiFlash, skip physically dropping it". However, it does not set the succeeded = false, so after all it will update the last_gc_safepoint.
When the whole cluster has few write commands, the gc_safepoint may not change. It make that the physically dropping only run after the gc_safepoint is changed again. Which will slow down the data disk reclaim.

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