Allow drop cache for Protobuf format

[AVMusorin]

Before it was impossible to update Protobuf schema without a server restart. With this commit, it is enough to send the query SYSTEM DROP SCHEMA FORMAT CACHE [FOR Protobuf].

Helpful for KafkaEngine and kafka_schema parameter.

Changelog category (leave one):

• New Feature

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

Allow to drop cache for Protobuf format with SYSTEM DROP SCHEMA FORMAT CACHE [FOR Protobuf].

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

Information about CI checks: https://clickhouse.com/docs/en/development/continuous-integration/

[Avogar]

Let's also support for CapnProto, should be easy to add

[AVMusorin]

Yes, it would be nice to add, but if you do not mind I can add it in the next PR?

[Avogar]

Sure, you can add it in the next PR

[robot-ch-test-poll2]

This is an automated comment for commit 8d0c961 with description of existing statuses. It's updated for the latest CI running

❌ Click here to open a full report in a separate page

Successful checks

Check name	Description	Status
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[clickhouse-ci]

This is an automatic comment. The PR descriptions does not match the template.

Please, edit it accordingly.

The error is: Changelog entry required for category 'New Feature'

[Avogar]

Please, add small documentation about new system query in system.md file and write a note about this feature in formats.md file in section about Protobuf

[AVMusorin]

Doesn't seem likely that failed 00385_storage_file_and_clickhouse-local_app_long is related to this PR.

[Avogar]

Just curious why you chose order SCHEMA FORMAT CACHE and not FORMAT SCHEMA CACHE. The second variant sound more natural for me.

[AVMusorin]

To be honest, I wouldn't say I like any of them (there are too many words in the query and it's hard to remember). But comparing them again, I can agree that the second variant might be more natural.

So, yep, I changed it.