various improvements

[akosyakov]

This PR contains the following improvements:

• diagnostics interruption to improve response time for other requests, as completion and signature help
• applied refactorings support
• suggest diagnostics support
• diagnostics buffering
• tolerating non-file URIs
• organize imports

[akosyakov]

• improve handling of cancel errors:

example: ts Server: (node:18925) UnhandledPromiseRejectionWarning: Error: Cancelled Request 122
example:     at token.onCancellationRequested (/workspace/typescript-language-server/server/lib/tsp-client.js:72:41)
example:     at CallbackList.invoke (/workspace/typescript-language-server/node_modules/vscode-jsonrpc/lib/events.js:71:39)
example:     at Emitter.fire (/workspace/typescript-language-server/node_modules/vscode-jsonrpc/lib/events.js:135:36)
example:     at MutableToken.cancel (/workspace/typescript-language-server/node_modules/vscode-jsonrpc/lib/cancellation.js:39:31)
example:     at CancellationTokenSource.cancel (/workspace/typescript-language-server/node_modules/vscode-jsonrpc/lib/cancellation.js:89:25)
example:     at LspServer.cancelDiagnostics (/workspace/typescript-language-server/server/lib/lsp-server.js:149:41)
example:     at LspServer.interuptDiagnostics (/workspace/typescript-language-server/server/lib/lsp-server.js:117:14)
example:     at LspServer.<anonymous> (/workspace/typescript-language-server/server/lib/lsp-server.js:314:39)
example:     at Generator.next (<anonymous>)
example:     at /workspace/typescript-language-server/server/lib/lsp-server.js:13:71
example: ts Server: (node:18925) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
example: (node:18925) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

• check an effect with Theia repo

[akosyakov]

@svenefftinge please review, I will do Rename File in a separate command, it is involving on Theia side