feat: replace go/importer with x/tools/go/packages

feat: support types.Array as interface args

chore: update Go, linter, CI, and dependencies

chore: fix CI

doc: add link to the article about Mocktail

chore: update linter

feat: generates returnsFn on function without args

chore: cleanup & update dependencies

fix: element from the same package

chore use go1.18