Bytes aggregations

[cyriltovena]

This adds two new range aggregations:

• bytes_rate which calculate the per second bytes rate of log streams.
• bytes_over_time which returns the bytes size of each log streams.

This can be used with filters, for example this query:

bytes_over_time({cluster="us-central1"} |= "err"[5m]) gives you the total bytes of logs containing the word err in the last 5 minutes.

Those two new aggregations are super useful to determine the size of streams sent to Loki.

Note for the reviewer: This PR brings a lot of code for extracting timeseries from stream which will be reused for future LogQL features.

Fixes #2077

[codecov-commenter]

Codecov Report

Merging #2150 into master will increase coverage by 0.14%.
The diff coverage is 90.38%.

@@            Coverage Diff             @@
##           master    #2150      +/-   ##
==========================================
+ Coverage   61.50%   61.65%   +0.14%     
==========================================
  Files         149      151       +2     
  Lines       11935    12006      +71     
==========================================
+ Hits         7341     7402      +61     
- Misses       4012     4019       +7     
- Partials      582      585       +3     

Impacted Files	Coverage Δ
pkg/logql/ast.go	89.42% <ø> (ø)
pkg/logql/engine.go	90.00% <ø> (-0.33%)	⬇️
pkg/logql/lex.go	100.00% <ø> (ø)
pkg/logql/evaluator.go	90.56% <81.81%> (-0.90%)	⬇️
pkg/logql/functions.go	87.87% <87.87%> (ø)
pkg/logql/series_extractor.go	94.28% <94.28%> (ø)
pkg/logql/range_vector.go	97.64% <100.00%> (ø)
pkg/logql/shardmapper.go	80.00% <100.00%> (ø)
pkg/logql/test_utils.go	89.13% <100.00%> (ø)
... and 1 more

[owen-d]

This is looking great, really looking forward to merging after addressing a few comments.