Report perf measurements from extension

We want to be able to track performance of language service operations to fix regressions and measure improvements (especially completions, go-to-definition, find-all-references, project loading, etc.). Whether this is middleware or generated server side is up for debate.

No files, tests, or entry points are named. Start by tracing how the extension reports language service operations such as completions, go-to-definition, find-all-references, and project loading, then clarify whether measurements belong in middleware or on the generated server side. Done means a decided reporting design that can track regressions and improvements for those operations.

Written by the indexing model from the issue text.