[.NET][JS] Update OAuth sample with FIC authentication

[ceciliaavila]

#minor

Description

This PR updates the .NET and JS 18.bot-authentication samples replacing the client secret with Federated Identity Credentials authentication. Aditionally, it updates the README files with the instruction to configure the Azure resources.

Detailed Changes

• Updated csharp_dotnetcore/18.bot-authentication to use FIC as the authentication method.
  • Upgraded botbuilder dependencies to version 4.23.0.
  • Added configuration steps in README file.
  • Configured FIC credentials in Startup.cs file.
  • Replaced MicrosoftAppPassword with MicrosoftAppClientId in appsettings.json.
• Updated csharp_dotnetcore/86.bot-authentication-fic sample to remove unused code.
  • Removed code related to ConversationState and UserState as it wasn't used anymore.
  • Updated targetFramework to NET 8.0 as the rest of the samples.
  • Corrected some details in README file.
• Removed old projects from dotnet solution.
• Updated javascript_nodejs/18.bot-authentication to use FIC as the authentication method.
  • Upgraded botbuilder dependencies to version 4.23.1.
  • Added configuration steps in README file.
  • Configured FIC credentials in index.js file.
  • Replaced MicrosoftAppPassword with MicrosoftAppClientId in .env.
• Updated javascript_nodejs/86.bot-authentication-fic sample.
  • Corrected some details in README and package.json files.

Testing

These images show the samples working after following the configuration steps.