Implement the more granular build cache

[galargh]

As the result of #5991 (https://www.notion.so/nomicfoundation/solidity-compilation-cache-17b578cdeaf580e3ba10c0d907fd6a4d), we cache compiler outputs per compilation job ID.

This is an optimal caching strategy for builds that do not merge compilation jobs (compilation job per root file) and builds in which none of the sources change.

As a follow-up, our cache should work effectively for builds in which only a subset of files being compiled change.

One possible solution to this, briefly explored during the initial cache implementation, is caching based on unmerged jobs. A POC of this solution was implemented in v-next...build-system-cache-v2

The next step on this is to create a design doc and open up a discussion about the implementation and required performance optimizations.