*wip* Query cache persistence

[rschu1ze]

Fixes: #58228
Fixes: #52141

30% done, not review-able yet. Uploading it as PR only in case my laptop catches fire.

The server now stores/loads the content of the query cache (i.e. cached query results) to/from disk during server shutdown/startup.

The data is stored in subdirectory query_cache/ relative to the base directory (<path>...</path>) in the server configuration).

To support future changes of the persistence format, a file query_cache/format_version.txt stores the version of the data, e.g. 1. Backward compatibility will likely not be implemented, i.e. future ClickHouse versions which support query cache persistence format versions > 1 will not be able to read earlier formats (existing data will simply be deleted).

In format v1, query cache entries are serialized like this:

• For each query result, a sub-folder is created, with the AST tree hash as folder name, e.g. query_cache/496d3a8d63e7/.
• [...]

Query cache serialization/deserialization can be enabled using a server setting (default: true):

<query_cache>
    <persist_cache>true</persist_cache>
</query_cache>

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[robot-ch-test-poll2]

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