Add default component name in constructor of AvroItemReader

[drow724]

public class AvroItemReaderBuilder<T> {

	private String name = AvroItemReader.class.getSimpleName();

AvroItemReaderBuilder's name field has defalut value (AvroItemReader.class.getSimpleName)

if (this.saveState) {
	Assert.state(StringUtils.hasText(this.name), "A name is required when saveState is set to true.");
}

so that assert code is never throw error because name field has default value

and i'm adding code that initializing name field to AvroItemReader.class.getSimpleName

[fmbenhassine]

remove useless assert state

This assertion is not useless. Here is a case where the name could end up being null or empty even with a default name in the constructor:

AvroItemReader avroItemReader = new AvroItemReaderBuilder()
		.name(getNameFromPropertiesFile())
		// set other properties
		.build();

In this example, if getNameFromPropertiesFile() returns null or an empty string, the reader will be created in an inconsistent state. That's why it is better to fail fast at the builder level.

[fmbenhassine]

Rebased, squashed and merged as 89e7616. I just reverted the assertion removal as I believe it is needed as explained in the comment above. Thank you for your contribution!