benchmark the time to perform a refactoring

[devoncarew]

We should benchmark a representative time to calculate a refactoring (a rename refactor for example).

We can use most of the framework of the existing pkg/analysis_server/benchmark/benchmarks.dart run analysis-server benchmark.

[bwilkerson]

Better yet would be to gather analytics data for these operations.

[devoncarew]

We are already gathering these analytics for internal users.

The benefit of a benchmark is that it would allow us to know at which commit a regression occurrs.

[srawlins]

And with Dart 3 we're gathering analytics from external users who don't opt out