tests/fuzzers: improve the fuzzers (#21829)

* tests/fuzzers, common/bitutil: make fuzzers use correct returnvalues + remove output

* tests/fuzzers/stacktrie: fix duplicate-key insertion in stacktrie (false positive)

* tests/fuzzers/stacktrie: fix compilation error

* tests/fuzzers: linter nits

common/bitutil/compress_fuzz.go

@@ -24,7 +24,7 @@ import "bytes"
 // invocations.
 func Fuzz(data []byte) int {
 	if len(data) == 0 {
-		return -1
+		return 0
 	}
 	if data[0]%2 == 0 {
 		return fuzzEncode(data[1:])
@@ -39,7 +39,7 @@ func fuzzEncode(data []byte) int {
 	if !bytes.Equal(data, proc) {
 		panic("content mismatch")
 	}
-	return 0
+	return 1
 }
 
 // fuzzDecode implements a go-fuzz fuzzer method to test the bit decoding and
@@ -52,5 +52,5 @@ func fuzzDecode(data []byte) int {
 	if comp := bitsetEncodeBytes(blob); !bytes.Equal(comp, data) {
 		panic("content mismatch")
 	}
-	return 0
+	return 1
 }