Search predicate for dependency search

Created by: malomarrec

• Define how exactly we will query dependencies via search (repo:deps(foo level=1) or dependencies:(foo level=1)?) or transitive:true
• Define what search results look like
• Do we need a new search result type (involve search product)? @quinnkeast @camdencheek @rvantonder
• Implement new search query syntax (involve search product)