feat(athena): Part 8 — run dbt unit tests on Athena

[aoelvp94]

Part of #16252. Related: #13822. Independent PR; the sequence is at the bottom.

Problem

Three Athena-specific gaps in the unit-test path, found by running a real project's 31 unit tests:

1. Schema inference. The default path materialises an empty temporary table via CTAS and introspects it. On Athena a zero-row Hive CTAS yields a table with no accessible columns (COLUMN_NOT_FOUND: Relation contains no accessible columns), and the probe would land under s3_staging_dir/tables/.
2. Type names. The Arrow-to-SQL table emitted Postgres spellings for Athena (text, float8, timestamp without time zone), which Trino rejects.
3. Integer widths. The table collapses every integer width into one name per backend. Trino's integer is 32-bit, so bigint fixtures overflowed (NUMERIC_VALUE_OUT_OF_RANGE).

Solution

• Athena joins DuckDB and ClickHouse on the query-schema path: the driver returns the result-set schema for ... where false limit 0.
• sql_types: Athena maps to varchar, double, timestamp, in line with dbt-athena's convert_*_type; bigint / integer / smallint / tinyint are kept distinct.
• get_field_sql_type_metadata_key Athena arm returns ATHENA:type, the key the driver emits.

Verification

• cargo fmt --check, cargo clippy -p dbt-adapter, cargo nextest run -p dbt-adapter -E 'test(athena)' clean on the pinned toolchain.
• On the real project: 15 of 31 unit tests pass; the remaining 16 fail for project reasons (an upstream table absent in that environment, and refs without a given fixture, which dbt-core resolves to the real relation and Fusion refuses). The latter is a documented Fusion/core difference, not raised here.

Feedback wanted: none beyond the code.

Sequence (independent PRs, each compiles alone against main)

• Part 0: feat(athena): Part 0 — map Backend::Athena to its driver entrypoint and send the driver's output-location option #16365 — ADBC driver wiring
• Part 1: feat(athena): AthenaDbConfig profile schema #16274 — AthenaDbConfig profile schema (@fpiped)
• Part 2: feat(athena): Part 2 — fill the parse-path todo!() arms and the config alias #16367 — dbt-adapter core wiring
• Part 3: feat(athena): Part 3 — accept partitioned_by, table_properties and force_batch as model configs #16368 — model config keys
• Part 4: feat(athena): Part 4 — vendor the dbt-athena 1.11.0 macro package #16369 — dbt-athena macro package
• Part 5: feat(athena): Part 5 — AthenaMetadataAdapter and athena_get_relation #16374 — AthenaMetadataAdapter and get_relation
• Parts 6+7: branch ready, not yet opened — Glue / Lake Formation housekeeping shims and the table / incremental helpers (athena/parts-6-7-execution); see also feat(athena): Part 6 — AthenaAdapter methods behind the dbt-athena macros #16376
• Part 8: this PR — dbt unit tests on Athena
• Part 9: feat(athena): Part 9 — dbt init profile wizard for Athena #16375 — dbt init profile wizard
• Full branch for context: https://github.com/aoelvp94/dbt/tree/spike/athena-profile-parse

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes.