Remove rreq local_blkd and merge alloc blks in data

[sanebay]

Remove rreq local_blkd() usage from raft_repl_dev and merge into one interface local_blkids().
mrege the two alloc_blks in repl_dev.h, e.g.

1. alloc_blks with MultiBlkId& out_bid
2. alloc_blks with std::vector<MultiBlkId>& out_bids