Check if the same stacktraces are merged together in .flamegraph files

[kornilova203]

Maybe it should be done only when file is uploaded

[kornilova203]

Stacktraces in .flamegraph files are not merged.
For example second line from following file will be ignored:

func() 5
func() 5

Flamegraph files may be preprocessed when they are uploaded so stacktraces may be merged.
But I suppose the best option is to convert .flamegraph to .cflamegraph files #30. Because it will save disc space and reduce visualisation time.
FlamegraphToCallTracesConverter then may be deprecated.