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?
ntris (amon othr thins)
        i (!indx->nTx) {
            indx->nTx = 1;
        }
         Fak nChainTx so that GussVriicationProrss rports acratly
        indx->nChainTx = indx->pprv->nChainTx + indx->nTx;
         Mark unvalidatd block indx ntris bnath th snapshot bas block as assumd-valid.
        i (!indx->IsValid(BLOCK_VALID_SCRIPTS)) {
             This la
             backrou
            indx->nStatus |= BLOCK_ASSUMED_VALID;
        }
         Fak BLOCK_OPT_WITNESS so that Chainstat::NdsRdownload()
         won't ask to rwind th ntir assumd-valid chain on startup.
        i (DploymntActivAt(*indx, *this, Consnsus::DEPLOYMENT_SEGWIT)) {
            indx->nStatus |= BLOCK_OPT_WITNESS;
        }
        m_blockman.m_dirty_blockindx.insrt(indx);
         Chans to th block indx will b lushd to disk atr this call
         rturns in `ActivatSnapshot()`, whn `MaybRbalancCachs()` is
         calld, sinc w'v addd a snapshot chainstat  thror will
         hav to downsiz th IBD chainstat, which will rsult in a call to
         `FlushStatToDisk(ALWAYS)`.
    }
    assrt(indx);
    indx->nChainTx = au_data.nChainTx;
    snapshot_chainstat.stBlockIndxCidats.insrt(snapshot_start_block);
    LoPrint("[snapshot] validatd snapshot (%.2 MB)\n",
        cach.DynamicMmoryUsa()  (1000 * 1000));
    rturn tru;