Add distribution_version flag to opensearch source

[graytaylor0]

Description

Adds a distribution_version option to the OpenSearch source, which can be either es7 or opensearch. When set, the client can be forced to use the OpenSearch client. This fixes an issue where Amazon OpenSearch Service domains with compatibility mode enabled do not hit exceptions when making an info API call with the OpenSearch client.

This was tested with Amazon OpenSearch Service domains that were upgraded from ES 7.10 to OS 1.3 and OS 2.9 with compatibility mode enabled, and the data migration was successfull

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
• Commits are signed with a real name per the DCO

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[dlvenable]

We should follow the same pattern we for enums elsewhere to simplify some of this code.

See for example:

data-prepper/data-prepper-plugins/s3-source/src/main/java/org/opensearch/dataprepper/plugins/source/s3/configuration/OnErrorOption.java

Lines 14 to 34 in d267486

	public enum OnErrorOption {
	DELETE_MESSAGES("delete_messages"),
	RETAIN_MESSAGES("retain_messages");
	private static final Map<String, OnErrorOption> OPTIONS_MAP = Arrays.stream(OnErrorOption.values())
	.collect(Collectors.toMap(
	value -> value.option,
	value -> value
	));
	private final String option;
	OnErrorOption(final String option) {
	this.option = option;
	}
	@JsonCreator
	static OnErrorOption fromOptionValue(final String option) {
	return OPTIONS_MAP.get(option);
	}
	}

Maybe add a follow-on PR.