Refresh connector samples (on main branch)

[bart-vmware]

Updated connector samples, based on default MvcWebApplication project template, targeting ~.NET 7~ .NET 6:

• CosmosDb
• MongoDb
• MySql
• MySqlEFCore
• OAuth
• PostgreSql
• PostgreSqlEFCore
• RabbitMQ
• Redis
• SqlServerEFCore

Review notes:

• Please ignore all changes below wwwroot. I just copied it from the default template, and there were/are no Steeltoe-specific customizations, as far as I'm aware.
• Due to the large amount of changes, GitHub is unable to properly match up old/new file names. Therefore I recommend to diff locally using a filesystem-based tool.
• The integration tests for CosmosDb, MongoDb, PostgreSql, PostgreSqlEFCore, and SqlServerEFCore fail due to #273. Because of time constraints, we've decided to address that later. Despite that, I've manually tested all of them, both locally and on CloudFoundry.

[TimHess]

This generally looks good to me. As discussed in the team call earlier today, if the samples in main can continue to target .NET 6 I think that is preferred for now. If that change introduces significant rework, then it would be OK to target .NET 7.

[bart-vmware]

This generally looks good to me. As discussed in the team call earlier today, if the samples in main can continue to target .NET 6 I think that is preferred for now. If that change introduces significant rework, then it would be OK to target .NET 7.

Locally they all work on .NET 6, except for the SQL Server sample. That's because it requires https://github.com/SteeltoeOSS/Steeltoe/pull/1094, but the pre-release version number on SteeltoeDev feed is incorrect, so it picks the stable v3.2.2 instead.

Update: The SQL Server issue was resolved by https://github.com/SteeltoeOSS/Steeltoe/pull/1096.