Easily accessible logger infrastructure for SwiftUI views

[Supereg]

Problem

This issue extends the discussion presented in StanfordSpezi/Spezi#80 to SwiftUI views.

As of right now there is no standard way to integrate logging capabilities into (reusable) SwiftUI views. While each view could just create their own Logger instance, this imposes the following problems:

• Simple UI components which are part of something "bigger" have a hard time justifying their own Logger instance with their own subsystem and category labels. Ideally, they would just use the Logger instance provided from their environment.
• The arguments discussed in the linked issue apply equally here.

Solution

This issue proposes a framework global logger EnvironmentKey which provides a strong default for an app-global logger.
Using this environment key, Individual UI components can then easily decide if they (a) inject their own Logger instance for all of their subviews (e.g., providing better defaults for the whole app, or something like SpeziAccount would want to inject it's own logger for all of its subviews) or (b) use the Logger from the environment which is particularly useful for small, reusable UI components like the AsyncButton.

Additional context

A PR addressing this issue would ideally integrate the new logging principles into all views, where applicable, SpeziViews already provides.

Code of Conduct

• I agree to follow this project's Code of Conduct and Contributing Guidelines