Fix processing lsif dump with repeating lines with inVs

Rewrite processing of lines with "label":"contains" and "label":"item" for appending for arrays instead override then when lines repeat few times with equal outV.

LSIF file for C-lang contains multiple contains entries:

{"id":48,"type":"edge","label":"contains","outV":9,"inVs":[47]}
...
{"id":60,"type":"edge","label":"contains","outV":9,"inVs":[59]}

instead of a single one:

{"id":48,"type":"edge","label":"contains","outV":9,"inVs":[47, 59]}

Let's accumulate contains references instead of overriding them.

Closes #305 (closed)