Remove all uses of IConfiguration and replace with IOptionsMonitor<TOptions>

[SaphireLattice]

See https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options?view=aspnetcore-8.0#the-options-pattern for documentation.

Could also use just IOptions as well

Will need minor shuffling of whatever consumes these, and some Startup things to make sure they get properly bound. And some config editing afterwards, probably.