Change all fs usage to be asynchronous

[bjaspan]

LanguageDefinition.ts uses readFileSync and existsSync from fs. The VSCode FS API for web extensions does not provide synchronous function calls: https://code.visualstudio.com/api/references/vscode-api#FileSystem. As far as I can tell from a little reading, it is not possible to implement a synchronous function out of an asynchronous function in typescript. Any function that wants to await on an asynchronous function return value must itself be async. So I think to support a web version of Cursorless we need to refactor LanguageDefinition, and all other uses of synchronous FS methods, into asynchronous code.

[AndreasArvidsson]

The vscode implementation of file system have now moved to be a synchronous. As far as I can tell all async implementations of fs are in scripts, test harness or the webpage.

cursorless/packages/cursorless-vscode/src/ide/vscode/VscodeFileSystem.ts

Line 52 in 4387672

await vscode.workspace.fs.readFile(this.resolveBundledPath(path)),