Add trec covid baseline queries

[lukuang]

In this PR I:

• add the query file for round1 of udel_fang_run3.
• add the query file for round2 generated the same way above
• add the python script to generate these files

[codecov]

Codecov Report

Merging #1142 into master will decrease coverage by 0.22%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1142      +/-   ##
============================================
- Coverage     47.91%   47.68%   -0.23%     
+ Complexity      715      705      -10     
============================================
  Files           144      144              
  Lines          8303     8303              
  Branches       1184     1184              
============================================
- Hits           3978     3959      -19     
- Misses         3988     4007      +19     
  Partials        337      337              

Impacted Files	Coverage Δ	Complexity Δ
...java/io/anserini/ltr/feature/CountBigramPairs.java	64.93% <0.00%> (-24.68%)	23.00% <0.00%> (-10.00%)

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[lintool]

What if we just kept query and removed question and narrative - just to reduce confusion?

[lukuang]

Effectiveness using the round 1 query in this PR:

• bm25: 0.5826

Effectiveness using different fields:

• query+bm25: 0.4099
• question+bm25: 0.5179

Experiments were done using Cord19AbstractCollection