Repository tidying?

[michaelpj]

I find the structure of the repository a little confusing at the moment. Here are a few suggestions:

• Move the lsp package to a lsp subdir.
• Make the bench and func-test packages components of lsp-test.
  • Yes, they're actually related to the lsp package, rather than being generic things that lsp-test provides, but that seems okay to me? It doesn't affect other users of lsp-test.
• Make the lsp-test/example package a component of lsp-test.
  • Possibly this wasn't done because you couldn't run it easily, but with Fix lsp-test example #298 you can.

Then we'd just have three packages in three top-level subdirs.

Happy to make a PR if this sounds good.