Ruler/loki rule validator

[owen-d]

Validates incoming loki rules according to logql instead of promql in the ruler.

[codecov-commenter]

Codecov Report

Merging #2589 into master will decrease coverage by 0.04%.
The diff coverage is 42.10%.

@@            Coverage Diff             @@
##           master    #2589      +/-   ##
==========================================
- Coverage   63.03%   62.99%   -0.05%     
==========================================
  Files         169      169              
  Lines       15005    15015      +10     
==========================================
  Hits         9458     9458              
- Misses       4795     4803       +8     
- Partials      752      754       +2     

Impacted Files	Coverage Δ
pkg/storage/stores/shipper/util/util.go	43.63% <0.00%> (-3.64%)	⬇️
pkg/querier/querier.go	62.71% <20.00%> (-0.37%)	⬇️
pkg/querier/queryrange/codec.go	87.18% <33.33%> (-0.38%)	⬇️
pkg/ruler/manager/compat.go	48.44% <42.85%> (-1.24%)	⬇️
pkg/querier/queryrange/roundtrip.go	71.83% <100.00%> (+0.13%)	⬆️