dts.pest: Add support for comments in devicetree source files

[pillo79]

Add support for comments in devicetree source files by extending the existing parser grammar. This is currently required to allow CI to pass on zephyrproject-rtos/zephyr#89410.

I have zero experience on Rust, but the COMMENT = syntax is taken verbatim from an example on the Pest website, and I also tried the change on the live editor there, so... I'm pretty hopeful 🙂

EDIT: CI passed on the manifest update PR (see message below)

[pillo79]

Above manifest update PR passed Zephyr CI on the Rust targets.

Compare with the errors with current v4.1-branch in the original PR when comments are not ignored by the Rust DTS parser:

Parsing zephyr.dts: Error { variant: ParsingError { positives: [label], negatives: [] }, location: Pos(11), line_col: Pos((3, 1)), path: None, line: "/* node '/' defined in zephyr/dts/riscv/qemu/virt-riscv.dtsi:15 */", continued_line: None, parse_attempts: None }

[pillo79]

@d3zd3z PTAL when you have the chance, thanks!

I based this on the stable branch for CI to pass on the Zephyr PR, but it's trivial to apply to main as well. Should I file a separate PR?