Update test runner documentation

[gustawlippa]

This PR updates the documentation of test runner. The main changes include correct examples (using existing presets) and rewording the ODBC parts in the documentation. It also includes fixes for small issues I noticed while reading the docs.

[chrzaszcz]

Looks good! I only have one comment.

[chrzaszcz]

Why remove this?

[gustawlippa]

My thinking was that the Driver and Setup variables (mentioned in the following lines) are set correctly for Ubuntu/macOS in the scripts. I was considering removing CentOS mentions altogether. But as you pointed out, I think there is no reason for removing this, I will revert this change.

[codecov]

Codecov Report

Merging #3087 (aa6f864) into master (8cfa47c) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head aa6f864 differs from pull request most recent head 73b0d8d. Consider uploading reports for the commit 73b0d8d to get more accurate results

@@            Coverage Diff             @@
##           master    #3087      +/-   ##
==========================================
- Coverage   78.84%   78.83%   -0.01%     
==========================================
  Files         377      377              
  Lines       31259    31259              
==========================================
- Hits        24645    24644       -1     
- Misses       6614     6615       +1     

Impacted Files	Coverage Δ
src/elasticsearch/mongoose_elasticsearch.erl	76.92% <0.00%> (-7.70%)	⬇️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	71.69% <0.00%> (-1.89%)	⬇️
src/mam/mod_mam_elasticsearch_arch.erl	86.60% <0.00%> (-1.79%)	⬇️
src/ejabberd_sm.erl	75.60% <0.00%> (-0.31%)	⬇️
src/mod_muc_room.erl	77.33% <0.00%> (-0.18%)	⬇️
src/ejabberd_c2s.erl	89.33% <0.00%> (-0.08%)	⬇️
src/mod_muc_log.erl	77.72% <0.00%> (ø)
src/ejabberd_s2s_out.erl	59.72% <0.00%> (+1.83%)	⬆️

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[chrzaszcz]

Nice!