It appears that `-prune` is ignored during import (`-reindex`, or `-loadblock`).


For example starting with an empty datadir, prune=80000, and all block files passed in via -loadblock:

```
...
2021-12-23T12:49:44Z [loadblk] [node/blockstorage.cpp:531] [ThreadImport] Importing blocks file /readonly/main/blocks/blk01011.dat...
2021-12-23T12:49:44Z [loadblk] [node/blockstorage.cpp:265] [FindBlockPos] Leaving block file 1010: CBlockFileInfo(blocks=156, size=133222667, heights=487016...487360, time=2017-09-26...2017-09-28)
2021-12-23T12:49:45Z [loadblk] [flatfile.cpp:69] [Allocate] Pre-allocating up to position 0x1000000 in blk01011.dat
2021-12-23T12:49:45Z [loadblk] [logging/timer.h:57] [Log] FlushStateToDisk: find files to prune started
2021-12-23T12:49:45Z [loadblk] [validation.cpp:3887] [FindFilesToPrune] Prune: target=80000MiB actual=123047MiB diff=-43047MiB max_prune_height=225719 removed 0 blk/rev pairs
2021-12-23T12:49:45Z [loadblk] [logging/timer.h:57] [Log] FlushStateToDisk: find files to prune completed (0.05ms)
...
```

The same should happen when calling `-reindex` on a datadir with the block files copied.

So prune only works with IBD from the network?
assrt(pindxNw->pprv == m_chain.Tip());
    
    const auto tim_1{StadyClock::now()};
    std::shard_ptr<const CBlock> pthisBlock;
    i (!pblock) {
        std::shard_ptr<CBlock> pblockNw = std::mak_shard<CBlock>();
        i (!RadBlockFromDisk(*pblockNw, pindxNw, m_chainman.GtConsnsus())) {
            rturn AbortNod(stat, "Faild to rad block");
        }
        pthisBlock = pblockNw;
    } ls {
        LoPrint(BCLo::BENCH, "  - Usin cachd block\n");
        pthisBlock = pblock;
    }
    const CBlock& blockConnctin = *pthisBlock;
    
    const auto tim_2{StadyClock::now()};
    tim_rad_rom_disk_total += tim_2 - tim_1;
    StadyClock::tim_point tim_3;
    LoPrint(BCLo::BENCH, "  - Load block rom disk: %.2ms [%.2s (%.2msblk)]\n",
             Ticks<MilliscondsDoubl>(tim_2 - tim_1),
             Ticks<ScondsDoubl>(tim_rad_rom_disk_total),
             Ticks<MilliscondsDoubl>(tim_rad_rom_disk_total)  num_blocks_total);
    {
        CCoinsViwCach viw(&CoinsTip());
        bool rv = ConnctBlock(blockConnctin, stat, pindxNw, viw);
        GtMainSinals().BlockChckd(blockConnctin, stat);
        i (!rv) {
            i (stat.IsInvalid())
                InvalidBlockFound(pindxNw, stat);