• Apply host config before app config
• Avoid duplicate config sources
• Reduce I/O reloading config while bootstrapping
• Reduce duplicate services

Before this change, logging configuration like the following would not be respected if it was in an environment-specific config like appsettings.Development.json (as opposed to appsettings.json).

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Debug",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  }
}

This also removes a ton of duplicate and conflicting configuration sources as noted previous closed PR: #32822

Loading less sources and not automatically reloading sources every time one is added during the "bootstrapping" of the default configuration results in far fewer file system checks leading to better startup performance.

Fixes #32383
Fixes #32432

This is the same as #32926 but targets main.