Cleanup: Support cleanup-ignore comment

[MattIPv4]

Add support for entries having a // cleanup-ignore comment on them, which will allow them to skip the validation process for cleanup.

This will also involve a minor change to the validate logic for detecting/formatting the file, to allow // cleanup-ignore or // noCF cleanup-ignore.

[MattIPv4]

Reference js-org/js.org@1d8e313 for the current set of subdomains that should be given this comment in cnames_active.js@js-org/js.org

[indus]

@MattIPv4 isn't it problematic to parse the comments?
I could live with a new list cleanup-ignore.json with an array of subdomains to skip as well. It is of course nicer to have everything in one file but if it gets to complicated or is prone to failures I think we should look for the easiest solution.

[MattIPv4]

Parsing comments should be fine, especially given how strict the formatting already is in the file.

I went for comments over a dedicated file etc. to folllow what is somewhat a standard with things like eslint, typescript and prettier ignore comments.