Only applies entry limits to non-SampleExprs.

[owen-d]

Two issues:

1. The docs were incorrect for -validation.max-entries-limit. 0 does not mean disabled.
2. We were incorrectly validating against the API limit param on metric queries. This didn't make sense so I've added a check and avoided this case.

[codecov-io]

Codecov Report

Merging #2850 into master will decrease coverage by 0.09%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #2850      +/-   ##
==========================================
- Coverage   61.37%   61.28%   -0.10%     
==========================================
  Files         179      179              
  Lines       14438    14443       +5     
==========================================
- Hits         8862     8851      -11     
- Misses       4766     4780      +14     
- Partials      810      812       +2     

Impacted Files	Coverage Δ
pkg/querier/http.go	0.00% <0.00%> (ø)
pkg/promtail/positions/positions.go	46.80% <0.00%> (-11.71%)	⬇️
pkg/storage/stores/shipper/uploads/table.go	68.66% <0.00%> (-1.85%)	⬇️
...kg/storage/stores/shipper/uploads/table_manager.go	65.78% <0.00%> (-1.76%)	⬇️
pkg/canary/comparator/comparator.go	78.18% <0.00%> (+1.81%)	⬆️
pkg/querier/queryrange/downstreamer.go	97.64% <0.00%> (+2.35%)	⬆️

[oddlittlebird]

Suggested change

	# Maximum number of log entries that will be returned for a query.
	# Maximum number of log entries that returned for a query.

[cyriltovena]

LGTM

[cyriltovena]

I don't think it's related to #2863