ucsi/v1_2/lpm: Introduce GET_PD_MESSAGE command

[RobertZ2011]

This is an optional command that was skipped in the initial implementation.

[Copilot]

Pull request overview

This PR introduces a new ucsi::v1_2 module (feature-gated behind ucsi-v1_2) and extends the UCSI v1.2 LPM command set with the GET_PD_MESSAGE command, including encode/decode plumbing and response support.

Changes:

• Move UCSI core types into src/ucsi/v1_2/ and gate them behind the new ucsi-v1_2 Cargo feature.
• Add GET_PD_MESSAGE command support in ucsi::v1_2::lpm (args, response data, command routing, tests).
• Add v1.2 CCI types and add SET_POWER_LEVEL command argument types.

Reviewed changes

Copilot reviewed 25 out of 27 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
Cargo.toml	Adds the ucsi-v1_2 feature flag.
src/ucsi/mod.rs	Replaces previous UCSI contents with a feature-gated v1_2 module export.
src/ucsi/v1_2/mod.rs	New v1.2 UCSI root module (command types, headers, command/response encoding/decoding).
src/ucsi/v1_2/cci.rs	New v1.2 CCI bitfield wrapper types.
src/ucsi/v1_2/lpm/mod.rs	Wires GET_PD_MESSAGE into LPM command/response enums, encode/decode, and tests.
src/ucsi/v1_2/lpm/get_pd_message.rs	New command definitions for GET_PD_MESSAGE (args + response data + tests).
src/ucsi/v1_2/lpm/set_power_level.rs	New command definitions for SET_POWER_LEVEL (args + tests).
src/ucsi/v1_2/lpm/*.rs	Updates imports to reference crate::ucsi::v1_2::* types.
src/ucsi/v1_2/ppm/*.rs	Updates imports to reference crate::ucsi::v1_2::* types.
src/ucsi/v1_2/ppm/state_machine.rs	Updates UCSI module imports to use the v1.2 namespace.