Databento-dbn

Breaking changes
- Renamed `VersionUpgradePolicy::Upgrade` to `UpgradeToV2` in preparation for a future
DBN version 3

Enhancements
- Added `v1` and `v2` modules to allow unambiguously referring to the record types for
a given DBN version regardless of whether the record type has changed. Previously
versioned aliases only existed for record types that have changed between DBN versions
- Added identical namespaces to `databento_dbn` Python package
- Changed `dataset()` method on `MetadataBuilder` to accept an `impl ToString` so now
`Dataset` and `&str` can be passed directly
- Added type aliases for `TBBOMsg`, `BBO1SMsg`, `BBO1MMsg`, `TCBBOMsg`, `CBBO1SMsg`,
`CBBO1MMsg` in Python

Deprecations
- Deprecated `dataset` module. The top-level `Dataset` enum and its `const` `as_str()`
method provide the same functionality for all datasets. This module will be removed in
a future version

Enhancements
- Upgraded `async-compression` version to 0.4.18
- Upgraded `proc-macro2` version to 1.0.92

Breaking changes
- Changed async DBN decoding to return `Ok(None)` when an incomplete record remains in
the stream. This matches the existing behavior of sync DBN decoding

Bug fixes
- Added handling for `UNDEF_TIMESTAMP` in `pretty_` timestamp getters for Python. They
now return `None` in the case of `UNDEF_TIMESTAMP`

Enhancements
- Added floating-point getters for price fields
- Added new IntelligentCross venues `ASPN`, `ASMT`, and `ASPI`
- Upgraded `thiserror` version to 2.0
- Upgraded `pyo3` version to 0.22.6

Bug fixes
- Fixed `pretty_activation` getter in `databento_dbn` returning `expiration` instead
of `activation`
- Fixed some `pretty_` getters in `databento_dbn` didn't correctly handle `UNDEF_PRICE`

Enhancements
- Added new `None` `Action` variant that will be gradually rolled out
to historical and live `GLBX.MDP3` data
- Added consistent escaping of non-printable and non-ASCII values when text encoding
`c_char` fields
- Implemented `Default` for `Action` and `Side`
- Added support for Python 3.13 to `databento_dbn`
- Implemented missing `Serialize` for (with `serde` feature enabled) for `Venue`,
`Dataset`, `Publisher`, `Compression`, `SType`, `Schema`, and `Encoding`

Enhancements
- Removed support for Python 3.8 in `databento-dbn` due to end of life

Bug fixes
- Fixed buffer overrun in `c_chars_to_str` on non-null terminated input

Enhancements
- Added Python type stubs for Record `__init__` methods

Breaking changes
- Combined `_reserved3` and `_reserved4` fields in `CbboMsg`
- Changed setters for `char` Record fields to accept a single-character strings
- Changed `rtype` and `length` to no longer be settable from Python. Users should
use the Record type `__init__` methods to initialize records

Bug fixes
- Added missing Python type stub for `CMBP_1` variant in `Schema`