Add a shared id to a chain of check commands

[foresterre]

e.g. The following events

{"type":"check_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"start"}
{"type":"setup_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"start"}
{"type":"setup_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"end"}
{"type":"check_method","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"method":{"type":"rustup_run","args":["1.35.0-x86_64-pc-windows-msvc","cargo","check"],"path":"..\\air3\\"}}
{"type":"check_result","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"is_compatible":false,"report":{"type":"incompatible","error":"error: failed to parse lock file at: ..\\air3\\Cargo.lock\n\nCaused by:\n  invalid serialized PackageId for key `package.dependencies`\n"}}
{"type":"check_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"end"}

Are all part of the same compatibility check. By giving it a unique id they can be more easily linked together.

What works today: Use the toolchain(.version) fields instead. They're the same within a chain.