…oft#498)

* rethrow exception after telemetry instead of disposing

* log an error instead of crashing when hitting some exceptions loading files, fix nullref when shutting down without an idle tracker

* fix short circuiting of question mark checks to prevent null from being returned

* print name of exception instead of relying on ToString

* don't use MaybeEnumerate

* upgrade message to Show

…set optimization (microsoft#517)

This isn't a complete fix, but does seem to improve microsoft#495 in some cases. Adds back the early MRO return removed in microsoft#277, so now large class hierarchies won't over-propagate types (where some of the trouble with fastai happens do to the Transform class). I also optimized AnalysisHashSet a little to do length checks when possible.

There are still times when things get caught up comparing unions for a while, but it seems to be nondeterministic.

- Fix microsoft#509: PLS doesn't flag error in a relative import if it is found in another root directory (microsoft#519)
- Fix microsoft#510: PLS doesn't resolve relative paths correctly

* catch exceptions when importing from search paths

* retry instead of not found