Remove in-memory data parts, part 3.

[alexey-milovidov]

Changelog category (leave one):

• Backward Incompatible Change

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

The obsolete in-memory data parts have been deprecated since version 23.5 and have not been supported since version 23.10. Now the remaining code is removed. Continuation of #55186 and #45409. It is unlikely that you have used in-memory data parts because they were available only before version 23.5 and only when you enabled them manually by specifying the corresponding SETTINGS for a MergeTree table. To check if you have in-memory data parts, run the following query: SELECT part_type, count() FROM system.parts GROUP BY part_type ORDER BY part_type. To disable the usage of in-memory data parts, do ALTER TABLE ... MODIFY SETTING min_bytes_for_compact_part = DEFAULT, min_rows_for_compact_part = DEFAULT. Before upgrading from old ClickHouse releases, first check that you don't have in-memory data parts. If there are in-memory data parts, disable them first, then wait while there are no in-memory data parts and continue the upgrade.

[robot-ch-test-poll1]

This is an automated comment for commit 78f8c93 with description of existing statuses. It's updated for the latest CI running

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Check name	Description	Status
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Check name	Description	Status
A Sync	There's no description for the check yet, please add it to tests/ci/ci_config.py:CHECK_DESCRIPTIONS	❌ failure
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Stateless tests	Runs stateless functional tests for ClickHouse binaries built in various configurations -- release, debug, with sanitizers, etc	❌ failure

[qoega]

1. How user can check if they have in memory parts?
2. How to migrate to not break tables if it had in memory parts?

I think it makes sense to add in docs/changelog