Store table schema in `SpaceInfo`

[pathscale]

Currently the table schema is not stored to data files when they are persisted. The data is just written using serialization from rkyv.

However, for the CLI tool that allows reading of the data files it is necessary to be able to read the data without prior knowledge of the schema. It is necessary to to add representation of the schema to SpaceInfo.

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Migrated from pathscale/wt-dead#24. Originally opened by @a-rodin on 2024-12-05T11:54:31Z.

[pathscale]

Confirmed open on origin/master: every generated and runtime SpaceInfoPage constructor still writes row_schema as an empty vector. Because 1.0 freezes expectations around persisted formats, acceptance is either populate and version the schema representation with reload/migration tests, or explicitly declare persisted files typed/opaque and close this CLI-oriented feature before release.

[pathscale]

Confirmed still open on the current PR #46 merge ref. An assertion that parsed SpaceInfoPage.row_schema be non-empty fails, and all four generated/runtime constructors still initialize row_schema: vec![]. PR #46 does not implement or version a stored schema representation.

[pathscale]

Resolved by #47. Generated persisted tables now store ordered row schema, primary-key fields, and secondary-index types in SpaceInfo; new stores install the metadata, non-empty mismatches are rejected, and legacy empty metadata remains readable without an implicit rewrite. Regression tests cover persistence, mismatch rejection, and legacy behavior.