fix: rank catalog configuration above table properties when constructing FileIO

[YuangGao]

Closes #3931

Rationale for this change

• Catalog._load_file_io computed load_file_io({**self.properties, **properties}, location) where properties is metadata.properties — table metadata outranked the catalog configuration.
• An operator sets catalog properties; anyone who can commit to a table sets table properties. The lower-trust source won.
• Reachable keys include implementation selection (py-io-impl, s3.retry-strategy-impl — dotted paths passed to importlib.import_module) and transport configuration (s3.endpoint, s3.proxy-uri, s3.signer.uri, gcs.service.host, the ADLS authorities).
• Table properties now rank lowest, still supplying keys the catalog leaves unset.
• REST precedence becomes table metadata < catalog < server config < vended credentials, so remote signing and credential vending are unchanged.

Are these changes tested?

• test_sql.py — covers Catalog._load_file_io through create_table / load_table.
• test_rest.py — covers RestCatalog._load_file_io, and pins server config above the catalog.

Are there any user-facing changes?

• A table property naming a FileIO key the catalog already sets no longer takes effect.
• Keys the catalog does not set still come from the table.