isis: publish spb capability

[fliqqs]

Initial extension to add SPB NLPID capability to Hello

Implement MT capability TLV and SPB service STLV's

[rwestphal]

@fliqqs Amazing work! Please rebase to fix the merge conflict (I changed the CI to use a different spell checker) and I'll merge this.

[fliqqs]

Addressed the review comments looks like the new spell check is not happy with ECT 😂

[rwestphal]

@fliqqs Thank you for the update!

Regarding the spell checker failure, please add an exception for "ECT" in _typos.toml. That should fix the issue.

We could configure the spell checker to ignore uppercase words, as most of the time they are valid acronyms. But that would probably be an overkill, as cases like this should be a rare occurrence. As of now, we only have three exceptions in the typos dictionary, which is sufficient for the entire codebase. typos does a much better job than cargo-spellcheck at avoiding false positives, but it's still not perfect :(

On a separate note, you could squash the third commit into the second one, since ideally every commit should compile and pass all tests. This helps when using git-bisect.