[exporter/elasticsearch] Update ECS mode encoder to add conversions for telemetry.sdk.language and telemetry.sdk.version

[isaacaflores2]

Description

This PR adds semconv conversion to Conversions map semconv attributes telemetry.sdk.language/telemetry.sdk.version to service.language.name/service.language.version'.

This is needed since the connector/elasticapm emit aggregated metrics with the above semconv attributes and without these conversions these fields are dropped from the metrics. This change will allow ECS aggregated metrics to match existing amp-data/apm-aggregation behavior

• https://github.com/elastic/opentelemetry-collector-components/blob/0d6ecf0/connector/elasticapmconnector/config.go#L186
  *https://github.com/elastic/opentelemetry-collector-components/blob/0d6ecf0/connector/elasticapmconnector/config.go#L216

Link to tracking issue

Fixes

Testing

Updated unit test cases

Documentation

Updated README.md

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