Feature request: log=livefanout

**Is your feature request related to a problem? Please describe.**
long lived shapes combined with lots of updated makes it almost unusable, a simpler solution than log compaction should be possible

**Describe the solution you'd like**
In general:
1. New clients connecting should always mean a new snapshot/sql query of the latest materialized view from the db
2. Keep a list of current offset of all clients. Remove logs with older offset than what the oldest client has
3. When TCP disconnects a client update the list of current offset of all clients and same as in step 2 remove logs with older offset than what the oldest client has