Improve MetadataService logging

[MasterKale]

This PR introduces a new logger argument to MetadataService.initialize(). This argument is of type SimpleWebAuthnLogger, which is a simple object of logging methods:

export interface SimpleWebAuthnLogger {
  debug: (message: string, ...args: unknown[]) => void;
  info: (message: string, ...args: unknown[]) => void;
  warn: (message: string, ...args: unknown[]) => void;
  error: (message: string, ...args: unknown[]) => void;
}

The intention is that projects using SimpleWebAuthn can define an instance of this interface that logs the message and arbitrary arguments in a way that makes sense for that project. This eliminates any SimpleWebAuthn-specific logging concerns that led to the old implementation getting ripped out of this project.

Right now only MetadataService will make use of this new logging pattern.

Fixes #751

[MasterKale]

Marking WIP for now until I write some tests. I'm otherwise happy with the current implementation.