Removed string from definition of KNet generic types

[masesdevelopers]

Description

Removed the use of <string, string> definition into KNet types moving to the .NET typed classes.

Related Issue

Closed #59

Motivation and Context

How Has This Been Tested?

Tested with available tests

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[mariomastrodicasa]

Testing the modifications introduced from this PR many times the test raises a java.lang.NullPointerException at

KEFCore/src/net/KEFCore/Storage/Internal/EntityTypeProducer.cs

Line 254 in 1608959

var future = _kafkaProducer?.Send(new KNetProducerRecord<TKey, KNetEntityTypeData<TKey>>(record.AssociatedTopicName, 0, record.Key, record.Value!));

The exception is raised after an uncertain number of iterations over the input of

KEFCore/src/net/KEFCore/Storage/Internal/EntityTypeProducer.cs

Line 237 in 1608959

public IEnumerable<Future<RecordMetadata>> Commit(IEnumerable<IKafkaRowBag> records)

The remote callstack reports:

org.apache.kafka.clients.producer.KafkaProducer.doSend(KafkaProducer.java:996)
org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:962)
org.apache.kafka.clients.producer.KafkaProducer.send(KafkaProducer.java:847)

[mariomastrodicasa]

Testing the modification introduced from this PR seems the speed of LINQ query is very poor; the following code

context.Posts.Single(b => b.BlogId == 2)

takes more or less 16 seconds to be executed as reported from the following output:
Elapsed context.Posts.Single(b => b.BlogId == 2) 16299 ms. Result is PostId: 2 Title: title Content: 2 BlogId: 2