[m3msg] Increase default writer initial backoff

[Antanukas]

What this PR does / why we need it:

Increases initial retry backoff from 1s to 5s for all M3Msg message writers.

Special notes for your reviewer:

Increasing initial backoff to 5s reduced M3Msg retries on all of our workloads to almost 0. Under normal conditions retries should be close to 0. On certain workloads we also saw CPU usage reduction in M3 Aggregator.

Motivation to set a new default is mainly because with current setting all clusters will experience more retries than needed.

The following metrics can be used to inspect if retries are happening:

coordinator_downsampler_remote_aggregator_client_message_retry
m3aggregator_aggregator_client_message_retry
m3aggregator_aggregator_flush_handler_message_retry

Does this PR introduce a user-facing and/or backwards incompatible change?:

NONE

Does this PR require updating code package or user-facing documentation?:

NONE

[codecov]

Codecov Report

Merging #3820 (29f95c5) into master (1c72e40) will decrease coverage by 0.3%.
The diff coverage is 100.0%.

❗ Current head 29f95c5 differs from pull request most recent head 734c27c. Consider uploading reports for the commit 734c27c to get more accurate results

@@           Coverage Diff            @@
##           master   #3820     +/-   ##
========================================
- Coverage    57.1%   56.8%   -0.4%     
========================================
  Files         552     552             
  Lines       63177   63081     -96     
========================================
- Hits        36115   35860    -255     
- Misses      23876   24020    +144     
- Partials     3186    3201     +15     

Flag	Coverage Δ
aggregator	63.4% <ø> (-0.3%)	⬇️
cluster	∅ <ø> (∅)
collector	58.4% <ø> (ø)
dbnode	60.4% <ø> (-0.4%)	⬇️
m3em	46.4% <ø> (ø)
metrics	19.7% <ø> (ø)
msg	74.4% <100.0%> (-0.1%)	⬇️

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[linasm]

Nit: no need for this comment, eventually it would go out of sync with the actual value.

[vdarulis]

m3msg producer retry options is one of the most confusing pieces of config around, thanks for the PR!