Promtail Helm Chart: Add support for passing environment variables

[tourea]

• Make Promtail's Helm chart support passing extra env variables
• bump charts versions

What this PR does / why we need it:
This PR enables developers to pass environment variables to the promtail containers via helm similarly to how it's done for loki

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated

[claassistantio]

All committers have signed the CLA.

[sandeepsukhani]

Thanks for the PR! I see a problem in setting the env var, added a suggestion with a fix for it.
Some other suggestion regarding bumping up of version.

@cyriltovena I would appreciate your thoughts on this since I am fairly new to helm charts.

[tourea]

@cyriltovena please review

[cyriltovena]

You have conflicts, also why do you need env vars in promtails ? I don't think we support any env vars.

[Demon-DK]

.... why do you need env vars in promtails ? I don't think we support any env vars.

Hi, @cyriltovena

But I guess env vars support are really required feature
Look at the example below. I'm feeling lack of this feature in such example.
For a while environments in this example haven't worked :(

[tourea]

@cyriltovena We also had to pass environment variables to promtail to make it work in our environments.
Rebased; please review

[codecov-io]

Codecov Report

Merging #1529 into master will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1529      +/-   ##
==========================================
- Coverage   61.84%   61.78%   -0.07%     
==========================================
  Files         109      109              
  Lines        8304     8304              
==========================================
- Hits         5136     5131       -5     
- Misses       2774     2777       +3     
- Partials      394      396       +2

Impacted Files	Coverage Δ
pkg/promtail/targets/tailer.go	73.56% <0%> (-2.3%)	⬇️
pkg/promtail/targets/filetarget.go	68.71% <0%> (-1.85%)	⬇️

[cyriltovena]

LGTM

all good now