Remove chain-joining thread-selection

[apfitzge]

Problem

• This feature helped in simulated traffic with forking/joining and txs were relatively cheap, but is not helping w/ mnb traffic where the txs are more expensive

Summary of Changes

• Remove this feature for the time being
• Removing this will increase the number of unschedulable transactions, but will also lead to better load balancing for our highest priority transactions.

Fixes #

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (47b4075) 81.8% compared to head (8f2f1b8) 81.8%.

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #34554     +/-   ##
=========================================
- Coverage    81.8%    81.8%   -0.1%     
=========================================
  Files         824      824             
  Lines      222486   222462     -24     
=========================================
- Hits       182090   182039     -51     
- Misses      40396    40423     +27     

[tao-stones]

lgtm