feat(functions): expose retry policies in Python and Rust (#4873)

Expose `FunctionRetryPolicy` on Function declarations and refresh
overrides, together with `error_policy` and recorded attempt counts.
Python uses the Rust validation rules before sending a request; local
refreshes reject these Enterprise options.

The policy bounds calls and backoff, supports
class/message/provider-code matching, and can disable retries with
`max_attempts=1`. Batch retry and skip operate on the whole failed call.
Requires Enterprise server support for the new policy.

Validation: rebuilt the Python extension; 47 targeted Python tests and
10 Rust tests passed. Python `make check`, Rust formatting, and `cargo
clippy --features remote --tests --examples -- -D warnings` passed. The
additional repository-root Ruff sweep reports existing errors under
`docs/web-tests`; the Python workspace checks pass.

Draft user guidance covers the supporting server requirement, safe
repetition of partial work and whole-batch exhaustion. The guide
sections stay hidden until release. Vale 3.24.0 passed for the added
draft prose; no paired deployed SDK/server retry acceptance was run.
Companion server: https://github.com/lancedb/sophon/pull/9812.

BREAKING CHANGE: Rust callers constructing `FunctionRegistrationRequest`
or `FunctionErrorRecord` with struct literals must supply the new
`retry_policy` or `attempts` field, respectively.

python/src/lib.rs

@@ -145,6 +145,7 @@ pub fn _lancedb(py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(table::tokenize, m)?)?;
     m.add_function(wrap_pyfunction!(permutation::async_permutation_builder, m)?)?;
     m.add_function(wrap_pyfunction!(util::validate_table_name, m)?)?;
+    m.add_function(wrap_pyfunction!(util::validate_function_retry_policy, m)?)?;
     m.add_function(wrap_pyfunction!(util::parse_field_path, m)?)?;
     m.add_function(wrap_pyfunction!(query::fts_query_to_json, m)?)?;
     m.add_function(wrap_pyfunction!(expr_col, m)?)?;