Build fails in Node 14 workflow

[augustjk]

Some node modules are not installed when running npm ci in node 14 which causes errors during the typescript build. Specifically vscode-languageserver, vscode-languageserver-textdocument, and vscode-languageclient are needed for the build to be successful.

See https://github.com/google/wireit/runs/6838811493?check_suite_focus=true

This is probably due to npm v6 not supporting workspaces and those dependencies are only listed in vscode-extension/package.json.

Potential solutions:

1. Reorganize the files so that language-server.ts and ide.ts and related tests could be part of the vscode-extension package (whose tests are not run in node 14)
2. Split them into a separate package like language-server
3. Configure the root project to have separate typescript builds so the test:headless can depend on that and run.

[rictic]

I think we could just make them dev dependencies in the main wireit package.json