feat: add ssts releated system table

[zhongzc]

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Depends on #6921

What's changed and what's your intention?

Introduces information_schema.ssts_*, a system table exposing SST file metadata to aid debugging and observability.

SELECT * FROM information_schema.ssts_manifest;
SELECT * FROM information_schema.ssts_storage;

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[killme2008]

It seems this information is for diagnostics or internal use. I’m not sure whether it belongs in the information schema or the greptime private schema.

@fengjiachun @sunng87 @evenyag WDYT

[evenyag]

LGTM. We can put them under the information schema, but only for debugging purposes, and don't provide guarantees about compatibility. We can mention this in the document.