Refactor GitHub source (#2379)

* refactor(github): cleanup logic

* fix(github): lookup wikis per-repo

* refactor(github): change scanErrs.String output

---------

Co-authored-by: Bill Rich <bill.rich@gmail.com>

pkg/sources/github/github_integration_test.go

@@ -53,11 +53,11 @@ func TestSource_Token(t *testing.T) {
 	}
 
 	s := Source{
-		conn:        conn,
-		httpClient:  common.SaneHttpClient(),
-		log:         logr.Discard(),
-		memberCache: map[string]struct{}{},
-		repoSizes:   newRepoSize(),
+		conn:          conn,
+		httpClient:    common.SaneHttpClient(),
+		log:           logr.Discard(),
+		memberCache:   map[string]struct{}{},
+		repoInfoCache: newRepoInfoCache(),
 	}
 	s.filteredRepoCache = s.newFilteredRepoCache(memory.New(), nil, nil)