.Net: Added implementation of Azure CosmosDB for MongoDB connector for new memory design

[dmytrostruk]

Motivation and Context

Related: https://github.com/microsoft/semantic-kernel/issues/6522

In this PR:

• Implemented IVectorStore
• Implemented IVectorStoreRecordCollection<TKey, TRecord>
• Azure CosmosDB for MongoDB default record mapper
• Options classes
• Extension methods for DI
• Integration tests  
• Unit tests

Contribution Checklist

• [x] The code builds clean without any errors or warnings
• [x] The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• [x] All unit tests pass, and I have added new tests where possible
• [x] I didn't break anyone :smile: