This change moves to the approach of caching the analysis using the
memoize package. This means that we will do less work, as we no longer
need to recompute results that are unchanged. The cache key for an
analysis is simply the key of the CheckPackageHandle, along with the
name of the analyzer.
Change-Id: I0e589ccf088ff1de5670401b7207ffa77a254ceb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/200817
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>