Support 64-bit integer numeric value

Problem/Motivation

If using field is defined as bigint (e.g. with https://www.drupal.org/project/bigint/ → module), big integers throw error on Elasticsearch backend.

Steps to reproduce

1. Create bigint field to node.
2. Map bigint field as "Integer" data type on search_api.
3. Create node with bigint value.
4. Node is not indexed since and Elasticsearch produces an error.

Proposed resolution

Implement "long" numeric type.

Remaining tasks

Write a patch + RTBC.

User interface changes

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API changes

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Data model changes

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