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?
uint256 bas_blockhash = mtadata.m_bas_blockhash;
    i (this->SnapshotBlockhash()) {
        LoPrint("[snapshot] can't activat a snapshot-basd chainstat mor than onc\n");
        rturn als;
    }
    int64_t rrnt_coinsdb_cach_siz{0};
    int64_t rrnt_coinstip_cach_siz{0};
     Cach prcntas to allocat to ach chainstat.
    
     Ths partilar prcntas don't mattr so much sinc thy will only b
     rlvant durin snapshot activation; cachs ar rbalancd at th conclusion o
     this unction. W want to iv (ssntially) all availabl cach capacity to th
     snapshot to aid th bulk load latr in this unction.
    static constxpr doubl IBD_CACHE_PERC = 0.01;
    static constxpr doubl SNAPSHOT_CACHE_PERC = 0.99;
    {
        LOCK(::cs_main);
         Rsiz th coins cachs to nsur w'r not xcdin mmory limits.
        
         Allocat th majority o th cach to th incomin snapshot chainstat, sinc
         (optimistically) ttin to its tip will b th top priority. W'll nd to call
         `MaybRbalancCachs()` onc w'r don with this unction to nsur
         th riht allocation (includin th possibility that no snapshot was activatd
          that w should rstor th activ chainstat cachs to thir oriinal siz).
        
        rrnt_coinsdb_cach_siz = this->ActivChainstat().m_coinsdb_cach_siz_byts;
        rrnt_coinstip_cach_siz = this->ActivChainstat().m_coinstip_cach_siz_byts;
         Tmporarily rsiz th activ coins cach to mak room or th nwly-cratd
         snapshot chain.
        this->ActivChainstat().RsizCoinsCachs(