Add input format One

[Avogar]

Changelog category (leave one):

• New Feature

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Add input format One that doesn't read any data and always returns single row with column dummy with type UInt8 and value 0 like system.one. It can be used together with _file/_path virtual columns to list files in file/s3/url/hdfs/etc table functions without reading any data.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

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[robot-clickhouse-ci-1]

This is an automated comment for commit 00865a7 with description of existing statuses. It's updated for the latest CI running
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The overall status of the commit is 🟢 success

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[alexey-milovidov]

Two questions:

1. Shouldn't we also have OneOutputFormat for consistency?
2. Is it possible to avoid even opening the file?

[filimonov]

It still can read a lot of data due to remote_filesystem_read_prefetch

[Avogar]

It still can read a lot of data due to remote_filesystem_read_prefetch

Yes, and also parallel read buffer can download some data in advance. Better to use settings remote_filesystem_read_method='read', max_download_threads=1 together with One format to avoid any data to be read (will be good to do it automatically)