Allow agent and debug bridge to be enabled by a configurable list of preprocessor symbols

[Kapusch]

Hi @Redth

Thanks for the Sherpa & DevFlow tools, they are excellent ideas!

I didn't experiment them yet (but I'm planning to), however I noticed the DevFlow agent and debug bridge may only be enabled based on the DEBUG preprocessor symbol. Am I correct? If yes, I thought it would be helpful to allow configuration for additional symbols (e.g., DEV, LOCAL) which by experience, are automatically defined when setting the element Configurations in the .csproj. This would make it more flexible and easier to integrate MauiDevFlow into projects with custom build configurations.

Suggestion:
Provide a way to define a list of preprocessor symbols (such as DEBUG, DEV, LOCAL) against which to enable the MAUI DevFlow agent.