Upgrade to ES2022 and use throw new Error instead of Promise.reject

[emlun]

This was originally motivated by one of the lints fixed in #278:

src/services/keystore.ts
  Line 619:6:  Expected an error object to be thrown  no-throw-literal
  Line 621:6:  Expected an error object to be thrown  no-throw-literal
  Line 626:4:  Expected an error object to be thrown  no-throw-literal
  Line 630:3:  Expected an error object to be thrown  no-throw-literal

I resolved this at the time by using Promise.reject instead of throw, because TypeScript is currently configured to output ES2016 code which does not have the cause argument in the Error constructor. But as explained in the ESLint docs for no-throw-literal:

It is considered good practice to only throw the Error object itself or an object using the Error object as base objects for user-defined exceptions. The fundamental benefit of Error objects is that they automatically keep track of where they were built and originated.