Expose LinkedIn B2B facets in /v1/ads/targeting/search

/v1/ads/targeting/search currently exposes only the interests facet for LinkedIn. The B2B facets that actually matter for our customers, industries, job functions, seniorities and company sizes, have to be passed as URN id fragments we
supply ourselves, and there is no way to search them by name.

Why it matters to us: we maintain our own static lists of LinkedIn's facet codes, currently 147 industries, 26 job functions, 10 seniorities and 9 company sizes. That means two things. We carry the risk that those lists drift from LinkedIn's
own tables without us noticing, and our users can't type "roofing" and get the matching industry, they can only pick from a list we happened to include.

What would help: name search over those four facets in the same endpoint, returning the URN we should pass back. We don't need anything clever, just lookup, so we can stop maintaining a copy of someone else's taxonomy.