Share functionality of placement building between components

[cthulhu-rider]

Object placement is build using netmap.Source and container.Source in most scenarios. Also there are some similar cases when we use same placement approach, e.g. shard evacuation introduced here and remote placement builder.

I propose to concentrate all placement functionality in single shared code space in order to easily reuse it in new tasks.

[fyrchik]

With a proper interface, tree server can use this component too.

[cthulhu-rider]

• 2674 brings foundation for this

• 2722 continues (they need to be sync)

caching is very meaningful for app performance and efficiency. Some attempts were made, but they are buggy, so lets also fix them

suggest to w8 4 prelim work finish