production/helm: Add projected and downwardAPI volume types to PodSecurityPolicy (#2355)

[StevenReitsma]

What this PR does / why we need it:
This PR adds the projected and downwardAPI volume types to the allowed list of volume types in the PodSecurityPolicy of the loki, promtail and fluent-bit Helm charts. See Issue #2355 for context.

Which issue(s) this PR fixes:
Fixes #2355

Special notes for your reviewer:
N/A

Checklist

• Documentation added N/A
• Tests updated N/A

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #2366 into master will increase coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2366      +/-   ##
==========================================
+ Coverage   61.46%   61.62%   +0.16%     
==========================================
  Files         160      160              
  Lines       13534    13534              
==========================================
+ Hits         8318     8340      +22     
+ Misses       4589     4568      -21     
+ Partials      627      626       -1     

Impacted Files	Coverage Δ
pkg/promtail/targets/file/filetarget.go	70.48% <0.00%> (+1.80%)	⬆️
pkg/promtail/targets/file/tailer.go	78.40% <0.00%> (+4.54%)	⬆️
pkg/promtail/positions/positions.go	60.71% <0.00%> (+13.39%)	⬆️

[cyriltovena]

LGTM

Maybe we could have made it optional by using extras.psp.Volumes, I'm fine with this for now unless someone complain in the future.