We will be able to split the LSP modules off later. These LSP modules
will provide the ability to write custom LSP servers and clients in
Swift. The sourcekit-lsp repository will build on top of this new
package to provide an LSP implementation that creates a language server
for Swift and C-based-languages.
On macOS since there is an override, both `measure` methods funnel
through one entry point, but on other platforms they are not `open`, so
we need to shadow all of them.
When running in debug, or in continuous integration that is not setup
for performance testing, default to not collecting performance metrics
to avoid failures due to slow or high-variability tests (default
max_stddev = 10% in xctest). Instead, run the measured block once and
skip the timing code. This has the nice side effect of speeding up test
runs in debug builds.
