Add fallback_formats for timestamp stage

[aminjam]

Which issue(s) this PR fixes:
Fixes #2590

Checklist

• Documentation added
• Tests updated

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

Merging #2615 into master will decrease coverage by 1.60%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #2615      +/-   ##
==========================================
- Coverage   63.13%   61.52%   -1.61%     
==========================================
  Files         169      169              
  Lines       15018    13154    -1864     
==========================================
- Hits         9481     8093    -1388     
+ Misses       4784     4322     -462     
+ Partials      753      739      -14     

Impacted Files	Coverage Δ
pkg/logentry/stages/timestamp.go	86.41% <66.66%> (-3.46%)	⬇️
pkg/promtail/positions/positions.go	46.80% <0.00%> (-12.85%)	⬇️
pkg/promtail/targets/file/tailer.go	68.53% <0.00%> (-10.63%)	⬇️
pkg/logql/step_evaluator.go	57.14% <0.00%> (-9.53%)	⬇️
pkg/logql/marshal/labels.go	66.66% <0.00%> (-8.34%)	⬇️
pkg/logproto/timestamp.go	40.00% <0.00%> (-6.81%)	⬇️
pkg/chunkenc/encoding_helpers.go	59.25% <0.00%> (-6.37%)	⬇️
pkg/logql/marshal/tail.go	66.66% <0.00%> (-6.07%)	⬇️
pkg/promtail/api/types.go	14.28% <0.00%> (-5.72%)	⬇️
pkg/logql/vector.go	81.81% <0.00%> (-5.69%)	⬇️
... and 160 more

[cyriltovena]

LGTM

@slim-bean if you're ok with the name of the property I let you merge it.

[cyriltovena]

@aminjam in the meantime can you sign the CLA ?

[sandeepsukhani]

LGTM. Thanks for the PR!

[slim-bean]

Hi @aminjam would love to merge this but we need to get the CLA "signed".

If you've "signed" it and it fails, this is usually because the email address in your commit doesn't match any in your github account.

Fixing this usually requires amending the commit with an email address you have in github and force pushing back to your branch.

Let me know if you have any questions or problems!

[aminjam]

Thank you all for your patience. I have been working through getting the authorization to sign the CLA. I hope to have more updates on the progress this week.

[slim-bean]

Nice thanks again @aminjam!