bug: lib/bots: fix names of private attributes

[ghost]

Make private members __is_multithreadable and __collector_empty_process protected members _is_multithreadable and _collector_empty_process to make them easily modifiable by Bot classes

fixes #2108

[codecov-commenter]

Codecov Report

Merging #2109 (0e7dd2a) into maintenance (d396543) will decrease coverage by 0.32%.
The diff coverage is 93.33%.

@@               Coverage Diff               @@
##           maintenance    #2109      +/-   ##
===============================================
- Coverage        76.04%   75.72%   -0.33%     
===============================================
  Files              427      427              
  Lines            22887    22585     -302     
  Branches          3046     3043       -3     
===============================================
- Hits             17405    17102     -303     
+ Misses            4778     4777       -1     
- Partials           704      706       +2     

Impacted Files	Coverage Δ
intelmq/lib/bot.py	62.08% <80.00%> (+0.03%)	⬆️
intelmq/bots/collectors/api/collector_api.py	53.33% <100.00%> (ø)
intelmq/bots/collectors/stomp/collector.py	37.14% <100.00%> (ø)
intelmq/bots/experts/splunk_saved_search/expert.py	20.75% <100.00%> (ø)
intelmq/bots/experts/threshold/expert.py	84.61% <100.00%> (ø)
intelmq/bots/outputs/file/output.py	49.35% <100.00%> (-0.65%)	⬇️
intelmq/bots/outputs/misp/output_api.py	24.00% <100.00%> (-0.76%)	⬇️
intelmq/bots/outputs/misp/output_feed.py	58.69% <100.00%> (-0.88%)	⬇️
intelmq/bots/outputs/tcp/output.py	31.57% <100.00%> (ø)
intelmq/bots/outputs/udp/output.py	41.86% <100.00%> (ø)
... and 245 more