Add sqlite.JSONB type for binary JSON storage (SQLite >= 3.45.0)

Added :class:`_sqlite.JSONB` type for SQLite's binary JSON storage
format, available as of SQLite version 3.45.0. Values are stored via
the ``jsonb()`` SQL function and retrieved via ``json()``, while the
Python-side behavior remains identical to :class:`_sqlite.JSON`.
Pull request courtesy Shamil Abdulaev.

Fixes: #13260

Adds `sqlalchemy.dialects.sqlite.JSONB` — a new dialect-specific type
for SQLite's binary JSON storage format, introduced in SQLite 3.45.0.

The type:
- renders `JSONB` in DDL (`CREATE TABLE t (col JSONB)`)
- wraps bind values with `jsonb()` on write, storing data as a BLOB
- wraps column reads with `json()`, returning standard text JSON to Python
- reflects back from the database as `sqlite.JSONB`
- behaves identically to `sqlite.JSON` on the Python side

SQLite 3.45.0 introduced a native binary JSON format (JSONB) that is
more compact and faster to parse than text JSON. Users who want to opt
into this storage format had no way to do so via SQLAlchemy.

- `JSONB` inherits from `sqlite.JSON` and defines `__visit_name__ = "JSONB"`
  so the DDL compiler dispatches to `visit_JSONB` instead of `visit_JSON`
- Added `JSONB: JSONB` to `colspecs` so the type is not remapped to
  `_SQliteJson` via the `sqltypes.JSON` MRO entry
- `bind_expression` / `column_expression` apply `jsonb()` / `json()`
  transparently; existing `result_processor` from `sqltypes.JSON` handles
  deserialization without changes
- Added `sqlite_jsonb` requirement (checks for SQLite >= 3.45 and that
  `jsonb()` is available, since it is a loadable extension)

`test/dialect/sqlite/test_types.py::JSONBTest` (8 tests):
- DDL renders `JSONB`
- Reflection returns `sqlite.JSONB`
- Round-trip read/write including `None`
- Sub-object extraction via `[]` indexing
- Compiled SQL shows `jsonb(?)` on INSERT and `json(col)` on SELECT
- `typeof(col)` returns `blob` confirming binary storage

Closes: #13261
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/13261
Pull-request-sha: 81b93af698e0222a9262614d39dd5ade6b640273

Change-Id: Ic38704674d30aa3d1bb5ce1e8ef5e4b0562ad91a