feat: auto-register ObjectStore and accept it in read/register methods

Closes #899. Integrates pyo3-object-store 0.9 to replace hand-rolled
store classes and adds two quality-of-life improvements:

1. **Auto-registration**: Every `read_*` / `register_*` call now
   invokes `try_register_url_store()`, which inspects the URL scheme
   (s3 / gs / az / http / https) and silently registers an appropriate
   `ObjectStore`. A guard (`object_store_registry.get_store()`) prevents
   overwriting a store the user already registered.

2. **Explicit store parameter**: All eight read/register methods on
   `SessionContext` now accept an optional `object_store` keyword
   argument. When supplied the store is registered directly (keyed on
   the path URL) before the operation runs; the auto-registration path
   is skipped.

Changes:
- `Cargo.toml` / `crates/core/Cargo.toml`: add `pyo3-object_store 0.9`
  workspace dependency.
- `crates/core/src/lib.rs`: replace hand-rolled store sub-module
  registration with `pyo3_object_store::register_store_module()`.
- `crates/core/src/context.rs`:
  - `register_object_store(url, store)` rewritten to accept
    `PyObjectStore` directly (no more `StorageContexts` enum).
  - New `prepare_store_for_path(path, store)` helper centralises the
    explicit-vs-auto dispatch.
  - `try_register_url_store` gains an early-return guard.
  - All eight read/register methods gain `object_store: Option<PyObjectStore>`.
- `python/datafusion/object_store.py`: rewritten to re-export
  `S3Store`, `GCSStore`, `AzureStore`, `HTTPStore`, `LocalStore`,
  `MemoryStore`, and `from_url` from `pyo3-object-store`, plus
  backward-compat aliases (`AmazonS3`, `GoogleCloud`, `MicrosoftAzure`,
  `Http`, `LocalFileSystem`).
- `python/datafusion/context.py`: all eight Python-side methods updated
  with `object_store: Any | None = None` and docstring entries.
- `python/tests/test_sql.py`: new integration tests covering explicit
  S3 store, auto-registered S3 URL, HTTP CSV, HTTPS CSV, and HTTPS
  Parquet (using public `coiled-datasets` bucket and GitHub raw URLs).

Author: mesejo

Cargo.lock

@@ -56,6 +56,7 @@ async-trait = "0.1.89"
 futures = "0.3"
 cstr = "0.2"
 object_store = { version = "0.13.1" }
+pyo3-object_store = { version = "0.9" }
 url = "2"
 log = "0.4.29"
 parking_lot = "0.12"

Cargo.toml

@@ -63,6 +63,7 @@ async-trait = { workspace = true }
 futures = { workspace = true }
 cstr = { workspace = true }
 object_store = { workspace = true, features = ["aws", "gcp", "azure", "http"] }
+pyo3-object_store = { workspace = true }
 url = { workspace = true }
 log = { workspace = true }
 parking_lot = { workspace = true }