feat: Commit offsets on subscription executor if sample rate is set to 0

[lynnagara]

Currently if the executor sample rate is set to 0 we don't send any events
through the processing strategy or commit any offsets. In our dashboards
the lag grows continuously dwarfing all other topics/consumer groups.

This adds a temporary workaround that just always commits offsets for every
message if the sampling rate is 0. We can remove it once we actually start
processing executor messages.

[codecov-commenter]

Codecov Report

Merging #2317 (c9c149a) into master (f06185a) will increase coverage by 0.05%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #2317      +/-   ##
==========================================
+ Coverage   92.72%   92.78%   +0.05%     
==========================================
  Files         558      558              
  Lines       25645    25649       +4     
==========================================
+ Hits        23780    23799      +19     
+ Misses       1865     1850      -15     

Impacted Files	Coverage Δ
snuba/subscriptions/executor_consumer.py	83.63% <50.00%> (-0.84%)	⬇️
snuba/clusters/cluster.py	94.87% <0.00%> (+1.70%)	⬆️
tests/migrations/test_runner_individual.py	100.00% <0.00%> (+1.76%)	⬆️
snuba/migrations/table_engines.py	98.76% <0.00%> (+2.46%)	⬆️
...nsactions_onpremise_fix_orderby_and_partitionby.py	84.00% <0.00%> (+2.66%)	⬆️
...ts/0010_groupedmessages_onpremise_compatibility.py	100.00% <0.00%> (+4.44%)	⬆️
snuba/optimize.py	90.69% <0.00%> (+6.97%)	⬆️
snuba/settings/settings_distributed.py	100.00% <0.00%> (+100.00%)	⬆️
snuba/settings/settings_test_distributed.py	100.00% <0.00%> (+100.00%)	⬆️

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