refactor(cache): split a getCached function out

[agilgur5]

Summary

Decent size simplification in tscache so that getDiagnostics and getCompiled call a common getCached function, which is just a tiny refactor of the code that getDiagnostics already had.

Details

• basically, refactor the getDiagnostics a tiny bit to also handle what the getCompiled function needs

  • then just call getCached from both instead
  • getDiagnostics and getCompiled were near identical except for the cache they used and checkImports, which are both parameters now
    • getCompiled also had a logging statement (called in both noCache and w/ cache branches), which was moved to before the call to getCompiled instead
    • the type param was composed into another function in getDiagnostics before the call too getCached now
  • this simplifies all the cache code to one main function now

• remove the markAsDirty call under noCache, as well, "dirty" has no meaning for noCache anyway

  • this simplifies that one if statement now too

References

• Note that checkImports is actually buggy per my investigation in Cache not invalidating declarations when import changes (need to use clean: true) #292 (comment)
  • I may end up removing it entirely as such, or at least setting it to true when declaration is true in getCompiled
• This was one of the bigger refactors that became easier to do once I completed other refactors (and got more familiar with this portion of the codebase) like refactor(cache): simplify clean method #358 etc
  • Still working on 1-3 more refactors of this portion of the codebase, which are all simplifications