Generate message size and cycle time consts

[felixvanoost]

Generates the following new constants per message:

• MESSAGE_SIZE in bytes. This avoids the overhead of using raw().len() or embedded_can::Frame::dlc() and makes the size known at compile-time.
• MESSAGE_CYCLE_TIME containing the value from the corresponding GenMsgCycleTime DBC attribute when it is present.

This PR should be stacked on top of #175.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/lib.rs	88.88%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

[felixvanoost]

@nyurik this is also ready for review now. :)

[trnila]

Works great!

embassy is using its own embassy_time::Duration type instead of core::time::Duration. Would it make sense to have this type configurable? The embassy type memory footprint is also smaller than the core one.

[felixvanoost]

@trnila Since the generated code will be integrated into projects using different timing libraries downstream (embassy-time, fugit, etc.), I think it makes sense to keep core::time::Duration here. Every timing library will have a constructor to ingest a core::time::Duration into its own types, and it keeps the number of optional arguments and coupling to 3rd-party crates lower in dbc-codegen. Perhaps we can look at adding support for more timing libraries as a separate issue/PR?