Fix encoding for Elasticsearch count pushdown

[bvolpato]

Description

We've identified that when a COUNT(*) query was pushed down and contained special characters, the QueryBuilder string was being handled as ISO-8859-1 and causing parsing issues for Elasticsearch.

Additional context and related issues

For example, this query:

SELECT COUNT(*) FROM catalog.default.users where country = 'Türkiye';

In case the "country" field is a keyword, would result in:

{"error":{"root_cause":[{"type":"parsing_exception","reason":"Failed to parse","line":1,"col":53}],"type":"parsing_exception","reason":"Failed to parse","line":1,"col":53,"caused_by":{"type":"x_content_parse_exception","reason":"[1:53] [bool] failed to parse field [filter]","caused_by":{"type":"json_parse_exception","reason":"Invalid UTF-8 middle byte 0x73\n at [Source: (org.elasticsearch.common.io.stream.ByteBufferStreamInput); line: 1, column: 64]"}}},"status":400}

The source for the problem was the new StringEntity(sourceBuilder.toString()), which uses https://github.com/apache/httpcomponents-core/blob/rel/v4.4.16/httpcore/src/main/java/org/apache/http/entity/ContentType.java#L106-L107 and defaults to ISO.

Release notes

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# ElasticSearch, OpenSearch
* Fix query failure for some queries when a predicate contains unicode text. ({issue}`issuenumber`)

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[martint]

The OpenSearch connector probably has the same issue. Can you apply the fix there, too?

[cla-bot]

Thank you for your pull request and welcome to the Trino community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. Continue to work with us on the review and improvements in this PR, and submit the signed CLA to cla@trino.io. Photos, scans, or digitally-signed PDF files are all suitable. Processing may take a few days. The CLA needs to be on file before we merge your changes. For more information, see https://github.com/trinodb/cla

[bvolpato]

The OpenSearch connector probably has the same issue. Can you apply the fix there, too?

Good call, yes, just reproduced there with the same set of tests. Pushed the same fix there.

I also applied the text blocks change/suggestions too, agree that it looks much cleaner. For context, I followed the same structure from the surrounding tests -- so they could likely get a similar refactoring.

[bvolpato]

Lastly, I've submitted the CLA, but I guess it might take a couple of days to hear back.

[pettyjamesm]

@martint - looks like this is just pending CLA processing before it can merge.

[martint]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!