Clean-up PDO and ADO types

[RobertZ2011]

• Fixed source flags are no longer a separate structure
• Introduce missing conversion functions where needed
• Add more tests

[Copilot]

Pull request overview

This PR refactors PDO and ADO types to simplify the codebase by flattening nested flag structures directly into their parent data structures and adding missing conversion functions. The changes primarily focus on eliminating the separate FixedFlags structure and improving type consistency in bitfield definitions.

• Merged FixedFlags structure directly into FixedData for source PDOs, eliminating an unnecessary layer of abstraction
• Updated bitfield definitions to use native bool types instead of u8 with manual conversions for boolean flags
• Added missing From trait implementations to convert data structures back to their raw u32 representations
• Changed visibility of internal Raw bitfield structures from pub to private
• Added comprehensive roundtrip tests for all PDO, RDO, and ADO variants

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/pdo/source.rs	Flattened FixedFlags into FixedData, updated FixedRaw bitfield to include all flag fields directly, made Raw structs private, added roundtrip tests for all PDO variants
src/pdo/sink.rs	Changed boolean bitfield types from u8 to bool, removed != 0 comparisons and as u8 casts, made Raw structs private, added roundtrip tests
src/pdo/rdo.rs	Added From<Rdo> and From<*Data> for u32 conversion functions, updated BatteryRaw and AvsRaw bitfield boolean types, made Raw structs private, added roundtrip tests for all RDO variants
src/ado.rs	Added From<Ado> for u32 conversion function, made Raw structs private, added roundtrip test for ADO

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