Drop metric with row key length bigger than BT limit

[malish8632]

This change will drop metric with row key length longer than 4096 bytes.
It will also create counter metric so we could alert on high numbers.

[lmuhlha]

Seems like checkstyle is still failing :(

[codecov]

Codecov Report

Merging #686 into master will increase coverage by 0.01%.
The diff coverage is 71.42%.

@@             Coverage Diff              @@
##             master     #686      +/-   ##
============================================
+ Coverage     53.88%   53.90%   +0.01%     
- Complexity     2962     2966       +4     
============================================
  Files           726      726              
  Lines         19426    19454      +28     
  Branches       1279     1282       +3     
============================================
+ Hits          10468    10486      +18     
- Misses         8513     8521       +8     
- Partials        445      447       +2     

Impacted Files	Coverage Δ	Complexity Δ
...istics/semantic/SemanticMetricBackendReporter.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...potify/heroic/metric/bigtable/BigtableBackend.java	90.38% <55.55%> (-1.25%)	59.00 <1.00> (+2.00)	⬇️
...oic/statistics/noop/NoopMetricBackendReporter.java	92.30% <100.00%> (+0.64%)	7.00 <1.00> (+1.00)
...m/spotify/heroic/test/AbstractMetricBackendIT.java	98.36% <100.00%> (+0.13%)	29.00 <2.00> (+2.00)
...com/spotify/heroic/aggregation/simple/MinBucket.kt	44.44% <0.00%> (-11.12%)	4.00% <0.00%> (-1.00%)

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[sming]

mainly just a compile-time alternative suggestion for the hugeRowKey flag and assertion - which only trips you up at run/debug time.

[sming]

LGTM