LCS repair: compact tables before making available in L0

When doing repair on a system with lots of mismatched ranges, the number of tables in L0 goes up dramatically, as correspondingly goes the number of tables referenced for a query. Latency increases dramatically in tandem.

Eventually all the copied tables are compacted down in L0, then copied into L1 (which may be a very large copy), finally reducing the number of SSTables per query into the manageable range.

It seems to me that the cleanest answer is to compact after streaming, then mark tables available rather than marking available when the file itself is complete.