Hoist fee collector id

[garious]

Problem

When I added leader scheduling to the bank, it sent the solana_runtime crate in an awkward direction where it's not clear what functionality belongs in the runtime and what's up at the protocol level.

Summary of Changes

Return to @pgarg66's original architecture, where the creator of child banks decide whom fees should go to. Rather than calling the pubkey leader_id, this PR calls it collector_id, hoping to further distinguish runtime from protocol. I'll send a follow-up PR to pull the leader schedule back up to the protocol level as well.

@rob-solana, fyi

[codecov]

Codecov Report

Merging #2945 into master will decrease coverage by 5%.
The diff coverage is 80%.

@@           Coverage Diff            @@
##           master   #2945     +/-   ##
========================================
- Coverage    78.3%   73.2%   -5.1%     
========================================
  Files         126     126             
  Lines       19604   20949   +1345     
========================================
  Hits        15355   15355             
- Misses       4249    5594   +1345