Support for TSServer Request Cancelation

[mjbvz]

#18053

Adds support for canceling ongoing TSServer requests using per request cancelation. This PR is a WIP currently.

@vladima and @mhegazy can you take a quick look at the PR to see if it looks correct. I keep getting error from the TSServer that look like this:

shell.ts:468 Error processing request. Mismatched request id, expected undefined, actual 4
Error: Mismatched request id, expected undefined, actual 4
    at Object.resetRequest (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/cancellationToken.js:57:27)
    at IOSession.Session.resetCurrentRequest (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/tsserver.js:73291:40)
    at IOSession.Session.executeWithRequestId (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/tsserver.js:73299:26)
    at IOSession.Session.executeCommand (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/tsserver.js:73305:33)
    at IOSession.Session.onMessage (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/tsserver.js:73325:35)
    at Interface.<anonymous> (/Users/matb/projects/vscode/extensions/node_modules/typescript/lib/tsserver.js:74477:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:188:7)
    at Interface._onLine (readline.js:232:10)
    at Interface.<anonymous> (readline.js:365:12)

It seems the expected request is never set. I think there is a bug on this line with currentRequestId = currentRequestId: https://github.com/Microsoft/TypeScript/blob/6117ed77087b5d84774ee545bd3cad3d059caa75/src/server/cancellationToken/cancellationToken.ts#L51

Here's a PR with a fix: microsoft/TypeScript#14594