Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

modules/indexer/code/bleve.go

@@ -392,7 +392,7 @@ func (b *BleveIndexer) Search(ctx context.Context, repoIDs []int64, language, ke
 
 	searchResults := make([]*SearchResult, len(result.Hits))
 	for i, hit := range result.Hits {
-		var startIndex, endIndex int = -1, -1
+		startIndex, endIndex := -1, -1
 		for _, locations := range hit.Locations["Content"] {
 			location := locations[0]
 			locationStart := int(location.Start)