* refactor!: Rename Logger to LogSink

And make LogContext take a LogSink instead of an OptionalLogger

Make the arguments to LogContext less overloaded. All of them are
optional but changed the order a bit to make it easier to use:

```ts
constructor(
  level: LogLevel = 'info',
  logSink: LogSink = consoleLogSink,
) {
```

Remove `tag`. You'll need to use addContext(tag) to get the same behavior.