Able to parse targets from a targets.log and not via "make -pRrq"

[andreeis]

Mentioned in #217.
Like we can parse for IntelliSense from a build.log and not invoke "make --dry-run", we should offer the same possibility to parsing targets: via a given "targets.log" and not by "make -pRrq".

[drok]

The build log "feature" was originally conceived as a workaround for non-working --dry-run. It should have been a temporary hack, because:

1. build logs contain old, probably outdated info.
2. Relying on build logs delegates the responsibility for updating these files to the end user, who is not necessarily a developer of the project, and not in a good position to take on this responsibility.
3. It adds unnecessary configuration complexity (from the end-user's perspective: WTF is a "build log"?)

The same logic applies to "target logs". Please don't make them into a "feature".

I suggest committing to remove this workaround. Take responsibility for a working, reliable --dry-run. I've already proposed #500. Further, I think time spent on maintaining the workaround rather working on actual deficiencies of this extension is time wasted. Please kill build logs with 🔥