ESQL tests: replace IT_test_only.csv-spec with required_feature

[nik9000]

Description

We end files with IT_test_only for ESQL's csv-spec tests to skip tests in our stripped down test runner, CsvTests, and just run them in our integration tests. We use required_features for versioning. Nik doesn't like the file ending version - it's not pretty! Let's use the required_featues for skipping CsvTests. It's pretty easy if you already have a feature - and if you don't, we should be adding those so we don't need the node version anyway.

Here's the list of files to rename:

• blog-IT_tests_only.csv-spec ESQL: Move a few more test out of IT_test_only #108377
• metadata-IT_tests_only.csv-spec ESQL: Rework integration-only csv testing #108313
• enrich-IT_tests_only.csv-spec ESQL: Move a few more test out of IT_test_only #108377
• docs-IT_tests_only.csv-spec ESQL: Remove remaining IT_tests_only #108434

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[nik9000]

All done.