build: enable unconvert linter (#15456)

* build: enable unconvert linter

 - fixes #15453
 - update code base for failing cases

* cmd/puppeth: replace syscall.Stdin with os.Stdin.Fd() for unconvert linter

swarm/storage/memstore.go

@@ -78,7 +78,7 @@ type memTree struct {
 func newMemTree(b uint, parent *memTree, pidx uint) (node *memTree) {
 	node = new(memTree)
 	node.bits = b
-	node.width = 1 << uint(b)
+	node.width = 1 << b
 	node.subtree = make([]*memTree, node.width)
 	node.access = make([]uint64, node.width-1)
 	node.parent = parent