Observations:
- In case of !requiresPosition we don't need to track position
- Also, in the latter case we don't need scopeKind (implicit contract)
- There were a lot of LookupInfo instances having two references
(fileName/scopeFqName) pointing to the same strings.
Looks like in common case (reasonable amount of files/fqnames) it's more
sensible to group lookups in the two-level-tree (implemented with nested maps)
It's expected to decrease memory consumption up to 15M in case of compiling
`idea` module in Kotlin project
Denis Zharkov
16a27d593c